Find the tensioner pulley on the passenger side of the engine.  It will be
the pulley farthest to the left when lookint at the engine from the front.
Put a 15mm socket with a long-handled ratchet on the bolt in the center of
the pulley, and turn the bolt clockwise.  The tensioner assembly will
rotate, and the belt will loosen.  Slip the belt off of the alternator and
adjacent idler pulley, creating enough slack so that you can gently let the
tensioner back.  Remove the belt.

To put the new belt on, start by looping it around the crank pulley (the one
on the bottom), and follow the belt routing diagram on the radiator core
support (should be a little sticker with the belt routing diagram).  When
you have the belt almost on, rotate the tensioner again so that you can slip
the belt over the tensioner pulley, then ease the tensioner back so it
stretches the belt tight.  Make sure that the belt is properly seated in all
the grooved pulleys (not hanging off of one edge or the other).

That's all there is to it...  start the engine and make sure it doesn't make
any funny noises, and you're all done.