Windshield wiper is stripped

The plastic cover has a tab on the bottom edge on the side opposite the wiper itself. You need a thin right angle pick or similar to catch the edge and pull it out, then it will pivot up on the end where the wiper arm rivet is. Be sure to apply a bit of lube at the pivot so the plastic can move, it is very thin and easy to break at the pivot end. Under the plastic you will find a nut that secures the arm to the wiper transmission stud. Remove the nut partway then tap down at the pivot to pop the joint apart. Most of the time the part that is stripped is the wiper arm end itself. There are a couple ways to repair it. The easiest is to use a stiff brush to clean out the knurling on the wiper stud, then add a washer under the nut so the nut has a bit of room to push the arm down farther before it bottoms out on the stud. The knurling is not very deep and strips really easy.