1. get a belt
2. get a 3/8 rachet
3. put the 3/8 rachet in the square hole in the tensioner pulley
4. if you're not strong enough to push just the rachet down to loosen the pulley, get a long regular wrench and slide the circular end over the end of the rachet to kind of extend the lever. that should give you enough leverage to loosen the tensioner pulley.
5. remove the old belt by pulling it off the idler pulley and just working it out of the engine bay, it may take a couple mins to figure out how to get it out of there. you have to slide it out from between the tensioner and the block. u'll understand what i'm talking about when u go to do it
6. resnake the old belt around the pulley's as shown on the diagram under your hood. if you dont have one i'll attach a pic of how the belt goes.
leave it off the idler pulley.
7. get the rachet and box end wrench out again and loosen the tensioner. that should give you enough slack to easily slip the belt over the idler pully.
8. make sure the belt is on straight on all the pulleys. you're done!
i just did this yesterday and it took me a while to figure out a way to loosen the tensioner. that biatch is strong! hope this helps.
in the pic, there should be the AC pulley on the right, but i think that person removed it. so if you have AC you'll have to work it around that too.