I sent one in May, here's my instructions from UD for reference:
"We have a redemption raffle that allows people to send in expired redemptions (autographed redemption cards from products 2005 and newer) to win a guaranteed prize. If you would like to participate in this redemption raffle please write your name, address, phone number, and email address on your redemption card and send it to the following address:
Upper Deck Company
Attn: Redemption Raffle
5830 El Camino Real
Carlsbad, CA 92008
Please make sure you put Attn: Redemption Raffle on the outside of the package. Any mail sent without an attention line will be shipped back to sender unopened."
I usually send tracked to UD just to make sure they receive it especially with the mail situation right now. Was about $13 from Southern Ontario.
Hope this helps.