If it's just a card for ten dollars, then you can use it to get ten dollars off a purchase. So just give it to the cashier when you finished getting everything, give the card to the cashier as he/she gets the things you are purchasing.
That card won't technically give you a catalog. You need to be a member of the Stuff Fur Stuff Club, and like the Admin posted on a thread earlier, you need to be listed to be mailed from your local Build-A-Bear Workshop. So, try talking to them about that.
Sorry if I may be wrong.