The Oxford Companion provides a succinct summary of Ephesians four in the following way:

(4.1-16) A call to unity prepares the way for an outline of the constitution of the universal church. The one and only God (Deuteronomy 6.4) has now revealed himself as Spirit, Lord (Jesus), and Father. The exalted Lord provides the church with diverse gifts to maintain its unity. The diversity of the members of his body supports its harmony. (4.17-32) The only way to affirm God's full revelation in Christ  is to make a radical break with non-Christian behavior and to put on Christ.

The writer's first call is that the believers 'walk worthy of the calling wherewith ye were called,"  and goes on to qualify that with "keeping the unity of the Spirit in the bond of peace." The writer then explains that through his ascension, Christ has led captivity captive and gave gifts; he says that he who ascended is the same one who descended into the lower parts of the earth. The writer then outlines what the gifts are and their purpose for building up the body of Christ. That body is built in unity, fitly framed and built in love. As members of that body, believers are to break with old behaviors, and the writer addresses again two ways: the "before" and "after" structure.

The writer, identifying himself as a prisoners, beseeches believers to walk worthily of their calling:

Eph 4:1 I therefore, the prisoner in the Lord, beseech you to walk worthily of the calling wherewith ye were called,

Eph 4:2 with all lowliness and meekness, with longsuffering, forbearing one another in love;

Eph 4:3 giving diligence to keep the unity of the Spirit in the bond of peace.

Eph 4:4 There is one body, and one Spirit, even as also ye were called in one hope of your calling;

Eph 4:5 one Lord, one faith, one baptism,

Eph 4:6 one God and Father of all, who is over all, and through all, and in all.

Walking worthily demands lowliness, meekness, longsuffering, forbearing one another in love, and giving diligence to keeping the unity of the Spirit in the bond of peace. The comes the unifying proclamation: "There is one body, and one Spirit,... one Lord, one faith, one baptism, one God and Father of all..."

Next, the writer of Ephesians  explains that to each one grace has been given: "Eph 4:7 But unto each one of us was the grace given according to the measure of the gift of Christ.  Then follows three verses on ascension/descension theology:

Eph 4:8 Wherefore he saith, When he ascended on high, he led captivity captive, And gave gifts unto men.

Eph 4:9 (Now this, He ascended, what is it but that he also descended into the lower parts of the earth?

Eph 4:10 He that descended is the same also that ascended far above all the heavens, that he might fill all things.)

Christ is the one who has ascended and led captivity captive and given gifts; that same one descended, and "He that descended is the same also that ascended far above all the heavens" for the purpose of filling all things. What the descension means has endured several interpretations:

8sn (4:9) The phrase the lower parts of the earth has been variously interpreted: (1) The traditional view understands this as a reference to the underworld (hell), where Jesus is thought to have descended in the three days between his death and resurrection. In this case, of the earth would be a partitive genitive. (2) A second option is to translate the phrase to the lower parts, the earth. Many recent scholars hold this view and argue that it is a reference to the incarnation. In this case of the earth would be a genitive of apposition. (3) A third option, which also sees the phrase of the earth as a genitive of apposition, is that the descent in the passage occurs after the ascent rather than before it, and refers to the descent of the Spirit at Pentecost (cf. Acts 4:11-16). Support for this latter view is found in the intertestamental and rabbinic use of Ps 68:18 (quoted in v. 8), which is consistently and solely interpreted as a reference to Moses' ascent of Mt. Sinai to "capture" the words of the law. The probability, therefore, is that Paul's comments here reflect a polemic against the interpretation of this passage in certain circles as a reference to Moses. See W. H. Harris, The Descent of Christ.

The writer in context here certainly refers to Christ as the one ascending and descending, and if Christ is also Jesus, then it refers to the incarnation.

Through the ascension has come grace and gifts: Eph 4:7 But unto each one of us was the grace given according to the measure of the gift of Christ." The primary gift is the gift of Christ, and subordinate to that are derivative gifts: "Eph 4:11 And he gave some to be apostles; and some, prophets; and some, evangelists; and some, pastors and teachers." These roles hold in common one purpose: the building up of the body of Christ.

Eph 4:12 for the perfecting of the saints, unto the work of ministering, unto the building up of the body of Christ:

Eph 4:13 till we all attain unto the unity of the faith, and of the knowledge of the Son of God, unto a fullgrown man, unto the measure of the stature of the fulness of Christ:

Eph 4:14 that we may be no longer children, tossed to and fro and carried about with every wind of doctrine, by the sleight of men, in craftiness, after the wiles of error;

Eph 4:15 but speaking truth in love, we may grow up in all things into him, who is the head, even Christ;

Eph 4:16 from whom all the body fitly framed and knit together through that which every joint supplieth, according to the working in due measure of each several part, maketh the increase of the body unto the building up of itself in love.

All are to mature into the "unity of the faith, and of the knowledge of the Son of God, unto a fullgrown man, unto the measure of the stature of the fulness of Christ."  The writer uses the organic full-grown man suggested in Ephesians two:

Eph 2:20 being built upon the foundation of the apostles and prophets, Christ Jesus himself being the chief corner stone;

Eph 2:21 in whom each several building, fitly framed together, groweth into a holy temple in the Lord;

Eph 2:22 in whom ye also are builded together for a habitation of God in the Spirit.

In Ephesians three, the organic metaphor is also used: "Eph 3:17 that Christ may dwell in your hearts through faith; to the end that ye, being rooted and grounded in love" The purpose is clear: the body of Christ, the church, is an evolving, growing and maturing entity: coming into being is a holy temple in the Lord, a habitation for God in the Spirit. Rooted and grounded in love for the common purpose of building a habitation for God, believers are to behave maturely, no longer being "tossed to and fro and carried about with every wind of doctrine. One remembers Nicodemus's consternation in John 3 and the reply of Jesus: 

Joh 3:5 Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.

Joh 3:6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.

Joh 3:7 Marvel not that I said unto thee, Ye must be born again.

Joh 3:8 The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth: so is every one that is born of the Spirit.

The wind blows, lists, and one hears it but cannot tell it origin or destiny; the metaphor is a natural one for the unseen, invisible power of the Spirit. The same metaphor interestingly is used for wind of doctrine; here, though, the wind takes on impact: tossing to and fro and carrying about. Certainly, in controversies about the law and grace, Moses and Jesus, the early believers are caught up in the highly charged psychological, social, political, cultural, and religious forces impacting them.

As mature members of the body of Christ, individuals are to walk worthily of their calling, to avoid old ways of formerly walking and to embrace new ways learned in Christ:

Eph 4:17 This I say therefore, and testify in the Lord, that ye no longer walk as the Gentiles also walk, in the vanity of their mind,

Eph 4:18 being darkened in their understanding, alienated from the life of God, because of the ignorance that is in them, because of the hardening of their heart;

Eph 4:19 who being past feeling gave themselves up to lasciviousness, to work all uncleanness with greediness.

Eph 4:20 But ye did not so learn Christ;

Eph 4:21 if so be that ye heard him, and were taught in him, even as truth is in Jesus:

Eph 4:22 that ye put away, as concerning your former manner of life, the old man, that waxeth corrupt after the lusts of deceit;

Eph 4:23 and that ye be renewed in the spirit of your mind,

Eph 4:24 and put on the new man, that after God hath been created in righteousness and holiness of truth.

One way is the way of vanity, darkened understanding, alienation from God, ignorance and hardness of heart, lasciviousness, uncleanness and greediness, corruption and lusts of deceit; the other way is the way of Jesus which demands putting away the former manner of life and being "renewed in the spirit of your mind," created in righteousness and holiness of truth. The new way demands reforming old behaviors:

Eph 4:25 Wherefore, putting away falsehood, speak ye truth each one with his neighbor: for we are members one of another.

Eph 4:26 Be ye angry, and sin not: let not the sun go down upon your wrath:

Eph 4:27 neither give place to the devil.

Eph 4:28 Let him that stole steal no more: but rather let him labor, working with his hands the thing that is good, that he may have whereof to give to him that hath need.

Eph 4:29 Let no corrupt speech proceed out of your mouth, but such as is good for edifying as the need may be, that it may give grace to them that hear.

Eph 4:30 And grieve not the Holy Spirit of God, in whom ye were sealed unto the day of redemption.

Eph 4:31 Let all bitterness, and wrath, and anger, and clamor, and railing, be put away from you, with all malice:

Eph 4:32 and be ye kind one to another, tenderhearted, forgiving each other, even as God also in Christ forgave you.

Old behaviors include falsehood, anger and sin, obedience to the devil, stealing, corrupt speech, grieving the Holy Spirit of God, bitterness, wrath, anger, clamor and railing, and malice; the new way is that of truth, unity, work that is good, giving to those with need, kindness, tender-heartedness, and forgiveness after the example of Christ. Reviewing this list of two ways, all of us will recognize ourselves and understand, the old is never completely distant from us and the new is a work in process.

Matthew Henry provides commentary upon Ephesians five not unlike, in emphasis, the above points, but the reader may enjoy the practical application.