any 1 know about APC tachs???cant get to light up???

[BLAZIN 70' BuGGiE]

I just got a early christmas present from my moms and i cant take the piece of shit back (she might cry).so iam gonna deal wit it for A while so i need to find out how to get this damn thing to light. its a Speed-Glo (Tach W/ Shift Light) (5”) Gauge (2 1/6") the model # is 10.7169.... theres some kind of inverter that came with it and no damn instructions on the inverter...The tack also has 2 black wires coming out of the back with no apparent use YET....the tach and shift light both work but aT night it dosne light PLEASE HELP........