Trading in my iphone

Select the phone that you want to buy from the top row of https://www.apple.com/iphone/

Then click the "Buy" button at the top right of the page for that phone.

Then click Yes for the question "Do you have a smartphone to trade in?"

You will pay full price for the phone. They will send you the new phone and a box for the old phone. You send the old phone back. Once they have the old phone and verify it matches everything you said online, they will refund your card the amount of the trade in.