Eurolite Gauges

Im having trouble installing my gauges. I installed my friends w/o a problem but mine seem a lil harder to wire. Theres 2 wires a red and a black wire....i found the parking light/headlight power wire and hooked the red wire to it and the black to another negative wire. But theres these other wires that confuse me. In the instructions it says wire the grounding metal sheet on the grounding screw. Does that mean to just put it to a bare screw? I tried that but it still didnt work. if anyone knows what to do with the grounding metal sheet please reply.