Chevrolet: 98 Chev, belt tensioner, joe joe

Question
my belt cam off on a 98 chevy cavlear. It looks like the belt tensioner is loose ( I think the bolt is loose ) I can not get the tenisoner back onto the housing to try to tighten the bolt, can you tell me what I need to do?
Thanks Joe

Answer
Joe;
HI wel if the belt came off, you might have some trouble as the belt comming off just threw the timeing out of place, but you might not have any trouble with it, you can use a 1/2 in breaker bar to put into the squre slot to hold the tension arm back, are you shure it did not break ?