If it is c-gear skins you want you must first have a dream world account, after that you must sync your black and/or white game(s) with that dream world account. Then you must find the code(i guess you already have them), with the codes you go to the promotion page of the GBL. Then you will find messages, find the promotion you have the code for and enter it there. It will be added to you GBL account and you must change it on the account. Then the next time you wake up a pokemon your c-gear will change to the one you picked
