There is an Allen bolt that holds the footrest on that comes in through the back of the footrest. You may have to remove the footrest hanger to access it.

Basically, undo the bolt that holds the footrest on and remove the footrest. The rear brake pedal rotates around the footrest. You will also have to unclip the brake pedal from the rear brake master cylinder, the return spring and the pressure switch that activates the rear light. Once you get the footrest off it is pretty easy to see what you have to do anyhow.