You probably need to contact the support and give them the key from your game dvd.
I did this with my three years old unopened AOC dvd last year.
I just asked them what to do with the dvd and they asked for the key.
I gave it to them and got the 30 days right away although I just wanted to know if I would.
As should be stated on the back cover of the dvd you get the 30 days only, if your account hasn't been premium before.
But I think this is true in your case, isn't it?
Leif - I had a pm from support that said I wasn't eligible for the 30-day offer with my particular upgrade. Dunno why, as I believe Amazon said the period was a part of the package.
But, I got two extra character slots and that's good.
While levelling you can collect AA xp and points and you can check out the forgotten city and breach instances from time to time (they scale, but not available for f2p as the AA points).
Of course only if you are premium at the time too. Otherwise you only unlocked the slow gain of AA xp through playing and usage of potions and books as well as the khitai race. Without premium you will get no additional content or playfields.