Spore steam proof - gifted

[low dome]

Hello,

My brother gifted me SPORE on Steam. I want to make an account. However, I don't know what proof I need for a gifted copy? I got him to send me the purchase history and receipt screenshots from him, but it was gifted to me and not bought by me ... How do I prove it is mine?

Also can I still try to get the account added even if it was purchased months ago? I gave up at the time because I couldn't figure out where to see what gifts I got from who.