The wiper arms have a spring-steel retainer on the backside of the arm. You can grab the wiper arm with your hand and squeeze that spring steel retainer while simultaneously prying the base off of the splined stud using a screwdriver. Apply the screwdriver between the top of the nut that holds the bezel to the cowl and the bottom of the wiper arm base. Twist the screwdriver and you will see the base begin to move upward off the stud. Once you get it up a little ways, you can pull it off by hand, but you must have the spring-clip in the back squeezed at all times while removing.