GPS sender for speedometer

I should have asked earlier then ha. I already have the dimmer, am just unsure about the wiring. It has the single white wire that goes to the gauge lights, and says it works multiple gauges.

I bought the classic dash wiring harness with my gauges. It has a single gray wire labeled gauge lightts that splits into 6 wires on the gauge side of the harness, one going to each gauge. Do I just splice the white wire from the dimmer to that gray wire before it splits off for each gauge?