Unplug the dryer from the wall to prevent shocks.
Remove the lint trap from the machine.
Remove the top panel of the machine by removing the screws that hold the lint trap door in place. Slide your screwdriver under the top panel and use it as a wedge to pop the dryer open.
Remove the back panel of the machine by removing the screws and allowing it to lean back.
Inspect the middle of the drum at the tip of the machine. Pull on the drum belt. If it comes loose, it needs replaced.
Remove the belt from the top of the tumbler. Reach your hand back to the bottom left of the machine and pull back the idler pulley to release the rest of the belt.
Fit the new belt around the tumbler, aligning the groove on the tumbler with the pointed end of the belt.
Reach back to loop the belt over the motor pulley. Bring the belt back under the motor pulley.
Position the belt over the top of the idler pulley, keeping it between the belt guides, then loop the belt back under the pulley.
Turn the tumbler a few times to make sure it is in place, then plug the machine in and test.