If you look at the second link diagram, there is a component called parking brake lever. That is also visable in the previous link, just to the left of the right shoe. It is connected to the top other right shoe and the cable pulls the bottom across to the left. The spreader bar is postioned between the top of the lever and the left shoe. When the bottom of the lever is pulled to the left, the spreader bar forces both shoes out to the drum.
