I have a 1990 Sahara that someone put the wipers horizontal. When in use, they would wipe water only to vertical and not all the way over the driver side field of view.
I took a small screwdriver (smaller than #2) and slid it into a small hole that is at the hinge of the wiper arm. Doing so released a clip and gave me better leverage to just slide the arm right off. I then rotated the wiper about 30* to my wanted angle, and slid the wiper back on. Finally removing the small screwdriver in the hole.