basically you turn the switch to on position, insert a pin through the front hole to depress another pin and then rotate the cover past the on position. it will pop the center out
but
the first thing you do is spray WD40 through the small hole in the front (with it in the on position).
next find a small drill bit or i use a torch tip cleaner and find a size that fits the hole.
don't just start pushing!!!! if you do you may jam the internal pin in the down position.
work the pin up and down in small increments until you reach the full stroke which is only about 1/8"
then with the pin depressed put light pressure past the on position and retract the pin at the same time.
the brass rings (or steel) are sometimes jammed. i have had some luck by heating one side with a butane torch then remove
