To install an idler pulley, there are a series of steps to follow, and it is important to use safety equipment since working with an electrical appliance. Start by unplugging the gas or electricity and removing the lint filter of the dryer.
Remove the lint filter housing, remove the screws, and lift the cabinet top by releasing the clips with a putty knife. Lift the top, and then disconnect the locking tab to remove the wire harness plug. Remove the front panel by taking off the mounting screws and lifting it up. Take a photo, if possible, of the configuration of the drive belt to refer to later.
Lift the front of the dryer drum to access the idler pulley, and push it to the right to release the tension on the drive belt. Remove the drive belt, and then pull the idler pulley away from the bracket and out of the dryer. Install the new idler pulley into the bracket, thread the drive belt through, and push the idler pulley to loop the belt over it. Put the front panel back onto the cabinet, reinstall the screws, and secure it to the cabinet. Reconnect the door switch wire harness, and reassemble the rest of the dryer. Plug the dryer back into the wall, and then turn on the gas if necessary before using the dryer.