belt tensioner on 2002 Pontiac Sunfire

how do i loosen the tension to get my serpentine belt on? what tools do i need?

2 answers
There is a proper tool ironically called a serpentine belt tool. This has a thinner head and longer handle to aid in the removal.
Looking at the instructions in a workshop manual it looks like the tensioner has a square "hole" at the axis of the tensioner wheel. Place I think a half inch maybe a 3/8 breaker bar in the hole and pry the tensioner gently in the direction in which allows the belt to get slack. Make sure you draw a diagram for yourself to show the correct routing of the fan belt.