Hello @JRk1234,
Welcome to AT&T and the Community Forums! Setting up your myAT&T account right away is a wise move. I can help you with this today.
We have a very informative article on how to create a myAT&T account. You should be able to set it up with the 10 digit phone number which was designated as the primary.
If it continues to ask for the account number you can find this on your first paper bill. This webpage will show you were to find it.
I will also be following up with a private message to your Forum’s Inbox. I look forward to hearing from you. Please have a fantastic rest of your day!
Jessica, AT&T Community Specialist