Random Username for on New Account

[takedownca1]

I have a family plan, and I just created a new account just to use on my Amazon Echo. I sent a family plan invite to a different email address and used the email link to create a new account. But now the username for that account is just a jumble of 25 random letters and numbers. Nnd now it seems I'm stuck with this username? And no, I have no desire to sign in with Facebook.