ok here is the problem i got 4 wires. white (ignition), black (ground), red (power for light), and green. now i know green is the main wire. im planning to put it in my truck. but i dont know where to put the green wire in my s10.

the truck is a 91 S10 2.8 5 spd. the tach is a Equus pro tach. it would help more if you have pics with it but someone help me so i can finish this

thank you in advance