How to send in my trade-in phone?

Hello,

I upgraded a phone, and part of the deal was to trade in my old phone.

i don't think i received any information regarding how to trade in my old phone.

i looked on my AT&T account, but also no info.

So - how do i send in my trade-in phone?

(i'm gavin (Edited per community guidelines), (Edited per community guidelines); the phone number w/ the trade in is (Edited per community guidelines))

thanks, gavin