Turn off the power to the washing machine by unplugging it from the wall.
Remove the access panel from the washing machine by unscrewing the holding screws. Some models may require that you tip the machine over to access the belts.
Unscrew the clamps that hold the belt coupling that connects the motor to the water pump. It will be a flexible rubber part. Remove the coupling.
Loosen the motor mounting bolts and push it inward to relieve the excess tension on the belt. Remove the old belt.
Put one end of the new belt over the transmission pulley before putting it over the motor pulley. Re-tighten the bolts on the motor and the coupling. Replace the access door of the washing machine and test the new belt.