How to add a campaign?

Hello tommorow i will receive the Nightfall Campaing...so i have a question...how can i add a campaing to my account?

I believe its at the login screen when you start the game,there should be a link that says "I have a new key" or something along those lines.

After you click on that link i believe it will ask you to log in again at some point before you finally add the key,or it will ask you if you want to make a new account or something like that, just make sure you choose to add it to an already existing account and to fill your login info correctly or you will end up with a seperate account unlinked to your current one.

or just login and click the 'Manage Account' button at the bottom left hand corner.

Note that you will probably want to ADD the campaign to the existing account, not start a new account with the code!

As above states

At log in just below your login name you will have the option to add a key

Please ensure it is added to your existing account.you will be prompted as you proceed through the procedure.

Take your time to ensure it added correctly as if you make an error and create a new account there is no going back.

and welcome to the nightfall campaign

The best way to make absolutely sure you add it to your existing account is to log in to your account first, then edit the account from the character select screen.