Representative payee - bank account set up

I have been named the representative payee for my adult child. I received a check with my name for the benefit of my adult child.
I tried to go to the credit union to set up an account and they said that there is a form that I need. I have no form. Just the original decision by the judge saying that my dependent "needed" a rep. payee. I showed them that document and gave them a copy of part of it. I don't feel comfortable (HIPPA) giving them the detailed report. They made copies of the two pages I gave them and sent them off and said that wasn't what they needed.
Called the SS office and left a message. Received several docs that outlined the scheduled payments and that I would be the payee, but no form to submit. Clearly I am the payee, the check is in my name.
Advice on setting up an account? Thank you. There is nothing online that I could find.