First remove the whole retractor/belt assembly from the car. Next you have to take the plastic cover loose from the spring on the belt shaft and carefully un-wind it by rotating it. Count the number of turns it takes to un-wind it. Once un-wound, remove the spring, then pull the belt all the way out. Remove the metal clip holding the belt to the belt shaft. Remove the belt, swap out the plastic cover, then re-install belt onto shaft. Re-install the spring and wind it back the same number of turns that it took to unwind it. Secure the spring and re-install the assembly into the car.