NEED HELP changing the serpentine belt on my 1999 Corolla.?

I am in the middle of changing the serpentine belt on my 1999 Corolla. I got the old belt off, but can%26#039;t seem to get the new one on . . . I can%26#039;t get the tension spring to compress enough to slide the new belt on. What am I doing wrong???|||first thing compare the 2 belts and make sure there the same size