If the mowing deck is attached you first have to remove the deck belt.
There is a diagram for the routing of the drive belt under the left foot rest. Push the brake pedal down and lock the parking brake. That will take the spring pressure off the idler pulley. Route the belt as the diagram shows. You may need to loosen one or more of the keepers that protrude along the sides of some of the pulleys to get the belt onto them. I find it best to start by putting the belt around the transaxle pulley first and working forward from there.
