hmmmmm............................
East to do hard to describe.
There is a spring that holds the wiper to the windshield, this force makes the splined portion want to push back against the shaft. making a straight pull difficult.
Lined up with the arm there a spring clip that barely sticks out from under the arm, this clip rides in a groove on the shaft, deflect this clip out from the shaft and pull the arm up off the shaft while trying to counter the force that holds the wiper on the glass. Using pry bar or screwdriver helps but usually damages the sheet metal cowl.
If you break something, I have some parts and the dealership should also, same wiper parts all the way to 1993.