Installing the belt on a Magic Chef dryer is tricky and there's no secret other than you can't have forearms like Popeye. You just have to get your arms skinny, close your eyes, and reach in with both arms. You know the routine -- push back the tensioner with one hand, thread the belt around the tensioner pulley and fish the belt around the motor pulley.
Before you installed the belt, did the drum turn easily? Are the front drum slides in good shape? Did you reinstall the rear drum rollers in the proper orientation?