Trade in after purchase

I purchased an iPhone 11 today at the Apple Store in Danbury, CT. The Apple specialist said that I could trade in my iPhone 6s from home using Apple Support. It states on your website that after purchase I will receive a trade in package. I'm not buying the iPhone on the internet; I purchased it at the store. How do I receive a trade in package to receive the $80 value; not the $40 value without purchase?