There's tab on the bottom of the wiper, that catches the splined head of the pivot. I use a small flat blade screwdriver to release it while wiggling the wiper free. Usually comes off pretty easy.
The arms are likely frozen in place, so a couple of light taps with a rubber mallet or a hammer (put a piece of wood between the cap and the hammer first) will help.
A little spring tab in the wiper arm has to release from the groove in the post. There is a special tool, but if you feel with your finger (it's usually under the actual arm side of the post), you will find it and then no need for the tool. Use a small screwdriver to move the tab away, while carefully pulling up on the cap from the other side (opposite the arm). Be careful, as it can pop off quite suddenly.