If you have already entered your registration info in your reservation, you will have to go through a Tesla SA to transfer reservations --- that is a pain and just depends on who you talk to for that.
If your have not filled any registration info, you can simply give your account/passwd as a part of reservation transfer.
In the case you may want to buy a MY eventually (after many months), you can just put your account on hold, and release the hold when you are ready to get the car (but you will still be in the queue waiting for a car).
Hope this helps. Good luck.