I can't figure out how to install a new drive belt on to the pulleys, can anyone help me?

<moved from Lawn & Garden>

You start by removing the belt from the engine to the deck, leave the deck belt itself alone it's the only one that doesn't need to be moved. Once the belt to the deck is gone lower the deck to the ground, it would be a cleaner job if the deck were removed but that not as easy as it might sound. It is best to have a helper sit on the mower while you slide unedr, have the helper depress the clutch so you can observe the operation of the spring loaded tensioner pulley as it relieves the tension. With the clutch held down you should be able to peel the belt off the engine. There may be keeper pins around some of the pulleys to keep the belt from ever jumping off by itself but you can squeeze between these pins.