serpentine belt change

how do you change the serpentine belt and what size sockets

What year?

If you have a 92 (or slightly newer) you will need an 18mm. I find that using a wrench is the easiest way. Just go buy one (most tool kits won't come with one). Using the closed end of the wrench, you simply put it on the bolt in the center of the round thing just below and towards the front of the car from the power steering pump. Have it facing the front of the car and as close to parallel to the ground as you can get and then pull up the wrench until the belt is loose enough to get it off the water pump pulley. Once it is off the pulley, let the wrench back down and then completely remove the belt. Installation is the opposite.