When people look at our life, if we claim the title Christian, do they see anything different than what they see in others who are not Christians? Paul has moved into the application section of Ephesians and tells us we need to live in such a way that others know who we belong to and what we stand for. Parents used to say you are a (fill in your last name here), so I want you to go out and do not bring shame to our name. That is what God is saying here, you are a Christian and I expect you to go out and live like one. If you have truly been saved, then live the way the scriptures tell you to live. Put off your old ways of conduct (old man), renew your mind by studying scriptures and put on the new man which is the way of living holy and righteous. Do people know who and what we are by the way we live?
Ephesians 4:17, 20-24 This I say, therefore, and testify in the Lord, that you should no longer walk as the rest of the Gentiles walk, in the futility of their mind, Eph 4:20 But you have not so learned Christ, 21 if indeed you have heard Him and have been taught by Him, as the truth is in Jesus: 22 that you put off, concerning your former conduct, the old man which grows corrupt according to the deceitful lusts, 23 and be renewed in the spirit of your mind, 24 and that you put on the new man which was created according to God, in true righteousness and holiness.