just add it. you won't lose your 10 day trial if thats what your on already.

when you upgrade from the trial account it starts your 30 days at the end of your trial time.

Just a lesson I learned the Hard way, don't upgrade digitally got to store and buy the game and imput the key, if you do it digitaly it takes up to 72hrs to remove all the trial restrictions on the account, if you input the key from a store bought version they come off instantly. Just FYI