I can't get my serpentine belt tight. Anyone have link to replace? Engine 3.4. on 2002 Chevrolet Monte Carlo

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
When I tighten the tensioner it seems like it is starting to get tight then it gets real loose again.
Is it hard to replace the Tensioner if its loose?
FYI I am not mechanically inclined.
Thanks for any response.
(1) Answer