Paul wrote the letter to the Ephesians sometime around AD 62, while he sat in Rome during his first Roman imprisonment. Ephesians is, therefore, one of the four letters commonly known as the Prison Epistles.
Ephesus was an important metropolitan city in the Roman Empire. Paul had ministered in Ephesus previously, as part of his third missionary journey (as told in Acts 19).
Ephesians has two distinct parts. In the first part (chapter 1 to 3), Paul places considerable emphasis on our position in Christ. These chapters summarize the good news of the Gospel and what our new identity is when we are born again and become believers.
In the second part (chapters 4 to 6), Paul explains the implications of our new identity for every aspect of our lives. Our faith, daily lives, and relationships are transformed when we build our lives on Christ, the Cornerstone.
Consider reading the whole of Ephesians in one sitting - before you read chapter-for-chapter in the reading plan.