As we transition into the second half of Ephesians, Paul wants us to put the truths he expounded on in the first half into perspective. The first three chapters have been very doctrinal; the final three chapters will be very practical. In other words, now that he has told us what God has done for us, he wants us to see what God wants to do through us.
Our role as believers is simply to allow God to use us as His hands and feet to do what He has already enabled us to do. Easier said than done, right? He has called each of us to something specific and significant, and He desires that our calling be lived out cooperatively among all the saints in the body of Christ.