Paul names himself as the writer of this letter to the believers at the church at Ephesus.
Except where noted, all instances of "you" and "your" refers to the Ephesian believers as well as all believers and so are plural. (See: [[rc://en/ta/man/translate/figs-you]])
Your language may have a particular way of introducing the author of a letter and its intended audience. AT: "I, Paul, an apostle ... write this letter to you, God's holy people Ephesus"
"In Christ Jesus" and similar expressions are metaphors that frequently occur in the New Testament letters. They express the strongest kind of relationship possible between Christ and those who believe in him. (See: [[rc://en/ta/man/translate/figs-metaphor]])