Just upload the single first, and then upload the entire album (including the single) as a separate release. Once the full release is in stores, you can choose to leave the single, or remove it and only have the album version available.
Note: If you use your existing ISRCs (you need to have the Musician Plus or Label plan to do so), the exact same audio file as in your original upload, same metadata (track titles, artist name, etc.) this might help retain play counts/playlists for the single in some stores. Nothing that we (or stores) can guarantee, however.