How do I replace the serpentine belt tensioner? on 2000 Chevrolet S10

It's making a loud rattling noise and my voltmeter shows erratic charging from my alternator. I suspect the belt tensioner isn't doing its job of keeping the serpentine belt tight thereby causing slippage on the alt. pulley. Appreciate any comments and/or advice on how to change out the belt tensioner.

1 answer
Loosen and take off belt at tensioner first. Should be simple- only one bolt holding it. Note some tensioner bolts turn opposite of normal loosening.