Applying another expansion?

Ok so i bought the first guild wars from the online store at PlayNc. But i have Nightfall from a store. So how exactly would i link nightfall with my online guild wars thing... Like if i install it is it automactic, or do i have to go do some stuff on PlayNc.

If any of you know just let me me know thanks.

Add the key to your original account. To do that, sign in to game, click on manage access keys. You want to add a key. You don't need to install the disc, just add the key.

go on create new account/add access key and add an access key to your new account

No! He already has an account. He just needs to add the key to the existing account.

Yeah, that link gives two options: Create a new account or add access key to existing account. Make sure to add a key to your existing account!