I own a couple of gages. One you just remove the cover/cap and then screw the gage on. The other one requires you to remove the valve before installing. I don’t believe either of mine came with directions. A wrench and a valve removing tool is all that should be required. What kind of gage did you get?
Not much to instruct you on. Just use teflon tape to seal the threads on the guage, install the actual guage part last, make sure it's tight and adjust it to th eangle you want.
So there's a special valve removing tool?
I bought a used fp gauge, it requires the removal of the stock valve in the rail.
Cool, thought that teflon tape might be required.