The arms are held on by that single nut (don't remeber socket size). After removing that nut, while with one hand pushing down on the hinged part to straighten it out, with the other hand pull up on the lower end of the arm to remove it from the stud.
Before you do this, be sure to remember the position of the blade so that you can put it back the same way. You might want to place a strip of masking tape on the windshield along the edge of the blade to mark its position before removal.
For paint, you'll want to get "Satin Black".
Installation is reverse of removal.