The windshield wiper arm and blade assembly is retained to the wiper linkage pivot by a locknut. The wiper arm will usually have a park position, that is, lift the arm away from the windshield to a point where the arm spring will hold it away from the windshield. Lift up the nut cover (where the arm meets the pivot linkage). Loosen the nut until the arm can be pulled off of the pivot. Put the arm on the pivot and tighten the nut. Close the nut cover and carefully lower the arm and blade to the windshield. The blade is retained to the arm by a clip or removal pin. Squeeze the clip, or twist the pin out of the retaining hole, depending on style.