You will need a 1/2" breaker bar with a handle at least 18" long. Locate the belt tensioner and release enough tension so that the belt can be safely displaced from the alternator or any other convenient
appliance. before removing the belt, make sure you make good notes on how the belt is to go back on ( or you may simply refer to the diagram under the hood). Remove the old belt. Thread the new belt into place, getting it ready for the last appliance in line. Displace the tensioner enough to safely attach the belt to the last pulley in line. Release the tensioner and remove the breaker bar. If the belt is correctly installed (make sure it is) then the job is done.
A further suggestion. I had a problem releasing the tension enough to reinstall the serpentine belt so I used an 18" long, 1" (id) black iron pipe as an extension for my breaker bar. It makes a world of difference and one person, even an old guy, can then de-tension the belt and slip the belt over the alternator pulley.
You will probably have to loosen the fan (the 13mm bolts on the fan clutch, not the 10mm going into the water pump) in order to get a 1/2" drive breaker bar on the belt tensioner. I recommend also removing the right (passenger side - on your left as you're leaning over the radiator!) idler pulley - a single 13mm bolt. Having that pulley out of the way makes it POSSIBLE to snake the belt down to the A/C compressor. Once the new belt is wound around all the lower components, heave over on that breaker bar (in the belt tensioner) and slip the belt over the top pulley last. Congrats! Take a sip of your fav beverage, and now have your buddy push on that breaker bar one last time while you put the idler pulley back in place with the 13mm bolt.
FYI, that idler pulley bearing goes out before anything else and may be the reason you're replacing the belt in the first place. $22 at AutoZone.
It only takes about five minutes to replace the belt, but it takes 30 minutes to get the fan out of the way and back on.