The first thing you need to do is remove the deck. Once you have the deck off you will need to remove the bolt from the large pulley on the bottom of the engine and slide the pulley down so the belt can be removed. There is a couple of idler pulleys half way back. Remove the belt from those first. Once you have it off of there you can then remove it from the front. There is a double pulley at the rear of the tractor. It is held on by a bolt through the transmission. You need to loosen that bolt so the pulley will shift enough to allow the belt to clear. Replace the belts as shown in the diagram and reassemble.