How do you release the tension on a serpentine belt for a 1998 Chevrolet S-10 truck?

It is quite easy, There is a spot to insert a 3/8" ratchet (No Socket) on the automatic belt tensioner. Simply use the ratchet like you normally would (I can't remember if you tighten or lossen to remove tension) and then use something like a block of wood or a helper to keep the tension off the belt to remove. The same to replace.