There is a drain plug on the bottom left front of the engine, Remove it and install the correct fitting to hook up the plastic water pressure line to. It is also a good idea to install a small valve closets to the engine before the plastic line incase the plastic line breaks at sea, you can close the valve and keep running.
Run it to the gauge and your done. Use ties to keep the line secure.
Do not tighten the plactic line with furrel to tight or it will cut the hose just snug it up.
You will not see pressure on the gauge when you hook up rabbit ears to a water hose. You will see pressure at around 25-30 mph running in the water. Do not exceed 25-30 psi.@ WOT. or 120mph which ever comes first. Some will tell you you can run 45-60psi but after you change a head gasket you would have wished you hadn't.
How it works, water pressure pressurizes the air in the line to read on the gauge, don't think you have to have water in the line to read pressure. You can acctually blow in the line and see pressure but you may turn blue.