Use Your Gamer Launch Account
Your account from any Gamer Launch site is valid here.
If you already have a Gamer Launch account connect your Facebook account on your user profile first before using Facebook connect to login. Otherwise you may end up with a new account.
In order to be eligible for the Core Hound Pup and the authenticator-protected guild rank, you will need to attach either a Battle.net Authenticator or a Mobile Authenticator to your Battle.net account.