turn the unit upside down. Notice that the knob on the side of the unit makes the front roller turn left or right, depending on direction of turn. (I had to use pliers to turn it). Turn the front roller so that the open end moves toward the motor, therefore shortening its distance to the rear roller. To get the new belt on the rollers, you must push the innermost part of the front roller (idler) against a solid object like a stud or work bench. (Mine required a good amount of force). You may have to use your body to push it so one hand is free to slip the new belt over the rollers. now the belt should go on at least part way. At this point you can release the force and turn the knob to rotate the roller so its close to parallel with the rear roller. I found that the belt will move onto (or off of) the rollers the rest of the way when the unit is on and spinning. Using due caution (dont lost an appendage) adjust the knob so the belt moves into proper position on the rollers. There may be a safer way, let me know if there is.