Are you talking about the full arm or the wiper blade?
If it's the arm as I suspect.
Pop the hood, take off the circular cap on each arm with a flat head screwdriver.
Wiggle, WD40 and use a good bit of patience to get the wiper arm off.
If you haven't removed them before they're likely frozen on and will take a few minutes.
Don't prize them up or you risk damaging the glass or bending the metal.