The General Manager mode (which can be played multiplayer against other GMs) slots you into the overlord position, where you'll need to keep your motley crew of wrestlers entertaining the masses. Once you've got your roster of wrestlers assembled, you have to decide which of them will be "clean" and which will be "dirty" - this is important because wrestlers have to be on opposite sides of the clean/dirty fence in order to fire up rivalries.
Speaking of rivalries, you're in charge of setting them up in a fashion that reminds us of when we were twelve and we'd put bees in a jar, shake up the jar and watch them fight to the death. Essentially, you'll select a storyline based on the quality of the writers (represented by a star rating) and then choose the key players in it along with the length of time you want it to go on. As time goes on, you'll see how your epics play out in the ring along with a healthy dose of cut-scenes and drama.
You can also check out how your wrestlers are stacking up on the Power 25. Their rankings are reflected in addition to a number of other important factors to their success. Mic Skills are useful for squeezing the best show ratings out of rivalries and promos while Injury Frequency will clue you into how fragile some of these behemoths really are.
If you're inclined to fire up your own customized wrestler, you can put them through the paces in the Velocity sub-shows in order to train them up before beating them down in title matches. There are also a variety of promos that you can run to boost the popularity of your wrestlers ranging from things as innocuously vulgar as bikini shows to out and out slander against rival General Managers or the wrestlers they manage.
Throughout all of this, the game allows you to simulate any part of the process to prevent you from getting stuck in spreadsheet hell. If you don't want to get so hands-on with the down-and-dirty day-to-day operation, you can always just have the game play that part for you - it'll make all the necessary decisions for you.