Place the head of a flat-blade screwdriver into the lower slot on the belt access door, located on the PowerSteamer Pro head.
Press down lightly on the screwdriver head to release the snap on the door. Repeat on the upper slot to release the upper snap and remove the belt access door.
Lift one side of the brush assembly out. Pull straight up to remove the brush assembly from the unit.
Replace one end of the new brush assembly by lining up the post on the brush assembly with the notch in the carpet cleaner.
Loop the belt around the opposite end of the brush assembly, pulling until the belt is tight. Push the roller into the vacuum cleaner and spin it to verify the belt moves easily. Close the belt access door.