I have a craftsman 18.5 lawn tractor and the drive belt has slipped off the rear pulley. How do I get it back on?

I had this problem often with my old Craftsman mower. First you need to push the clutch/brake pedal down and lock the parking brake. This will hold the pedal down and keep the tension off the belt so you can maneuver it. Getting the belt back on the pulley can be tough. You can do it by getting your hands up around the rearend to get it back on. But, it is much easier if you take the rear panel off the back of the mower. This will give you total access to the rear pulley and belt.

More info needed for complete answer.
Need Model number from under the seat.
Which belt? Wheel drive, or deck drive?

Victor