There is no such thing as an “Episcopalian–at–Large”. Every baptized person belongs to a specific community, a congregation which has a name and an address.
The congregation in which you were baptized, confirmed, or received is where your membership resides unless you have, at some point in your journey as an Episcopalian, requested that a formal Letter of Transfer be sent to some other parish. You may have lived in a community for years and have been active in the life of a church for all or part of that time but you are still a member of the congregation in which your records are kept.
It is a simple matter to move your letter. You need only to make the request that it be transferred. That is done by speaking to one of the clergy or calling the church office. The transfer then becomes a simple transaction between church offices, and you will be notified when it is completed.
To request a transfer from one congregation to another does not sever ties of affection or friendship with your former parish or mission church. In fact, it helps them keep their records accurate because they must still count you, although absent and inactive, while St. Luke's cannot count you as a member. And there are rights and privileges attached to formal membership, namely the right to vote in and to run in the vestry elections at the Annual Parish Meeting.
If you would like to officially become a member of St. Luke's through a Letter of Transfer from another Episcopal church, or through Confirmation, or Reception by the bishop, please contact one of the clergy or call the church office.