If it's the same one I have, there's a lever on the bottom with a knob, and you have to raise the lever to slide from the viewing side to the shooting side. Also, on the shooting side, you need to use an older, non-metering 4x5" back, if you want a groundglass back on the right side, otherwise it won't work in the horizontal position.
Also, you might look at the stops on the rod used for sliding from one side to the other to make sure they are in the right place, if it's not working properly. Once you see how the stops work, the operation of the back should be clear.
I also think this back doesn't work with the F, because the lever on the back interferes with the swing lever on the rear standard, or something along those lines.
I use it on my 8x10" P with a Norma-era 8x10 to 4x5" reducing back as shown in the attachment.
I've also attached a grid overlay that can be printed out on overhead projector film for the groundglass on the left side. I adapted it from one of Dave Parker's overlays on
www.satinsnowglass.com