In your receipt it will have the code. Go to account management and go to redeem codes and enter it there. Oh forgot to add it will ask you to download the costumes. You might have skipped it so either try again or check Playstation store it might just be there but it will say free instead of whatever price it has if any.
Did you try the playstation store? You have to download them before they appear in game. After you enter the code it offered to download them.
amazon also gives you a receipt. its in that cardboard envolope they sent you the game in. Look for it if not contact them.