Mark the location of the two holes on back to where you want to mount it on the wall. Drill out the hole so that the plastic mounts fit, screw the screws in leaving enough of the screwhead exposed to catch onto the 655 holes. Use the big holes on the 655 to go over the screw heads and then slide it over to secure it. If it is loose on the wall tightene the screws a little more, if you can't fit the 655 onto the screws loosen them up a little.
One trick you can do to make sure that the holes are in the correct place is to take a piece of paper and lay it on the bottom of the 655, then punch out where the holes are, then use the paper to mark where to put the holes on the wall.