You dont. Tesla will add it to your account. They normally dont add it till right before (or during) delivery, since they dont want people honking the horn, etc.
Based on what this OP states, they already own the car and are awaiting transport to their location, which is different from what you are asking.
@hcdavis3 you just have to wait until the day of delivery, it will show up either shortly before, or shortly after you sign the papers and the local delivery center pushes the button to add it to your account.
Back to the OP. Tesla's do go into a low power mode when their battery gets low. if I could make one recommendation to you it would be to STOP trying to conact the car through the app. Every time you "wake the car up" you increase the amount of energy lost, and if its in a low power mode (possible) because of low main battery, you do not want to do anything that would draw extra power for no reason... and "checking on the car" qualifies as no reason in this case.
I would contact the transport company and tell them you are concerned about the main battery being low, and ask them if they could plug it in to re charge it.