I got an email with the serial number for the AD2 stuff from Cakewalk after I redeemed my coupon code.
I launched the xlnaudio installer and clicked the register button and added that coupon code.
Then it prompted me to pick 3 things from 3 categories and I did.
I wasn't too fussy about it. I have a lot of drums and don't prefer AD2 all the time. Sometimes. And frankly, I really only use the drum beats on practice tracks. Sometimes I look through their EQ settings and stuff when mixing a live recording of a friend playing drums.