if this is a front loading washing machine then I assume you have it pulled out, removed the back panel and can see the motor and the large pulley on the back of the drum. If you get the belt around the spindle on the motor first and then begin to run it around the edge of the large pulley. When it begins to get tight then pinch the belt hard on to the pulley and then rotate it so that the belt is pulled completely onto the pulley.
Richard
March 2009