How do you pay the monthly fee for World of Warcraft?

One way is to buy the game at a store. You need regular World of Warcraft to play, but you can buy extensions in addition to that. Then put the disc into your computer and load it. When you are finished and the play screen comes up, go to your battle.net account at worldofwarcraft.com. Click Account management in the menu at the left. It should say upgrade or type in a CD Key. Click that one and type in the all caps code that is on your disc slip. Now you are ready!