Question on installing factory vacuum gauge

[Rich69shortfleet]

I just bought a factory tach and vacuum gauge conversion for my 69 C10 instrument cluster. Connecting the tach is pretty straightforward, but I'm confused about the vacauum gauge. The gauge does not come with any fittings but has a long threaded nut on the fitting on the back of the gauge which I'm assuming helps hold the gauge to the cluster. Anyway, I assumed there would be fittings along with it to connect a vacuum line hose from the gauge to the engine. There was nothing and there were no instructions.

I don't want to damage my new gauge so I'm asking. Is the way to connect it to find a screw on fitting for the back of the gauge with a barbed nipple that can connect to a vacuum hose that can then be routed to the engine's manifold vacuum? I can't imagine it would be any more complex, but I wanted to make sure. Not sure why such a needed fitting wasn't supplied.