The OE metal style you need to bend slightly backward to get the tension off the spring. Then gently rock it off the stud.
The newer design (Anco, Trico, etc...), you need a small screwdriver to push the small plastic retaining tab away from the stud. If you use the access hole ontop of the wiper, you will be pressing down.
I see you got it off, just wanted to say something for the others...