Should just be able to go to your profile/account, that's what I did way back when.
Just make sure after you do, you actually switch it over. When I first became a gold member I still looked like just a registered member because I didn't see you need to click an option to actually be seen as a gold member (and I assume other types) after you sign up for that service. Hope this helps. It'll probably get moved to the Tech and Support forum but, no worries.