You have to get the key and login to an SOE account via web browser and enter the key there.

It's not a registration to install/launch as it is an entitlement on the account.

Try www.soe.com and login then goto my Account and there should be a place to enter the code near the bottom. Once that's claimed try to login via the game. It really shouldn't allow you to start the game if you don't have the key on the subscription already though.. EQ2 never did and told me `No Subscription` when I had an all access pass but no key entitlement for the game itself.

If that all makes sense.. sorry, not much sleep :D