When you are checking out. You will see a page asking for your card details etc. Below there is a box. Put the code there.Also, those who got the code, have you been buying regularly and is the code the same as the one posted?
I suggest you take some time and browse through the earlier pages in this thread. You will be able to see what the different brands offered during a particular season. Even though you won't see pictures/details of all, the handful that caught the attention of the Ballers would have been posted/discussed. Just post if you have any doubts whatsoever.