i was wanted to know how to hook up an after market tack in a 1988 ford f-150 and thsi htack has a red white black and green wire so i could use some help

 

TACH ...short for Tachometer

Red to power
Either white or green to RPM signal on coil
Either whie or green to Tach Light
Black to Ground

 

What brand is it? I am going to guess and say the black is ground, the red is power, the white is the lightbulb for the dial, and the green goes to the negative terminal of the coil for the signal. If you have a small battery charger, you can hook it up to that and test it out. If you get the power worked out, take the green wire and brush it against the + or the - lead of the charger, and the needle should flicker up.