Whirpool Model #DDE6500GALAD. I have removed the back access panel and can see the drum belt and two pulley wheels through which the belt is threaded. I do not see any way to tighten the belt or do not know how to replace the belt if it needs replacing. Any ideas??

Double check that model on the inside rim of the door. Whirlpool has a decent support site but that model # is not coming up. If that is the correct model # I'd call them at Call 1-866-698-2538 to see if they can direct you.

Also, it could be the rollers that the dryer turns on. When those get worn, they can sweak too.