I think you are talking about the 500 coupons. They are sent randomly to your email address, you are not guaranteed to get it however if you do get it. When you click the "buy ap" page, Choose a method of payment, then click Proceed. Then there should be an option down bellow stating
" Have any gift cards, gift certificates or promotional claim codes?
Enter your coupon here:"
This is the place where you would add the promotional code which is given in the email.