those wipers are on a spline and the arm pulls up off the splined post, they make a special tool to take them off so you don't scratch your paint but I use a rag and a screwdriver to pry it up off the spline.
Don't have one here to look at but I am pretty sure it is the type that has a small lever on the top (windshield) side, near the base of the arm. You need to use a small screwdriver (or similar) to move the lever out about 1/8 inch; it should stay there. Then wiggle the arm to lift it up and off. Make sure to push the lever back in when done.
