I assume you're talking about a dash gauge, not the test instrument. What brand is it?

Generally, you connect the Hot (red) wire to the "accessory" side of the ignition switch and ground (black) wire to ground. You can Google "76 Camaro ignition switch" for a wiring diagram. An inline fuse on the hot side is an excellent idea. The light in the gauge is wired the same way.

I'm guessing you could Google your gauge mfg and part number and find a diagram also. That's easier than waiting for someone on a forum to look it up for you.