Swimmers who were previously registered with a different USA Swimming program, other than EMAC, must fill out and send in a transfer form. Typically, an administrator from EMAC will inform you if you need to do this. The type of transfer will determine whether there is a $10 fee, or not.
The Transfer Form can be found HERE.
If you represented another USA team, you must be "unattached" for 120 days since the day that you last COMPETED with that team. You may not swim any relays while unattached. LSC codes are from the area that a team is registered in. EMAC is in Middle Atlantic and the code is "MA". The team code is "EMAC". For a list of LSC Codes, go HERE. You can check the map at the top of the page, and scroll down to the list of LSC's. The code is in the far column on the left side.