Craftsman ridiing lawn mower 42" 15.5 hp mode #917270613 belt?

I was mowing and my riding lawn mower quit mowing the lawn! When I tried to figure out the problem it appears that the blade is moving up until I tried to mow grass that was thick. I checked the belt and it was really loose so I figured I would replace the belt. I replaced the belt and now when I try to engage the blade the belt is burning and shredding at the top!!! I think maybe the belt is too tight, but can not figure out how I need to loosen the tension, or if this was the problem in the first place? Any help would be appreciated