help with installing a tach?

i hope you guys can help me. i've got a 94 cavalier 2.2L. how would i go about hooking up a tach in it? on the back of the tach it has 4 wires. a red one, black one, light gray one, and a darker gray one. i know that 2 of them are for the light in the tach i just dont know how to hook it all up.

do you already have a tachometer on your car?

I will tell you it is a pain to install one, I just did it to mine. There are other ways, but the way I know to install one is to get under the car. It is best if you put your car on a lift. Under your car, you should look for your engine, in the same area where your spark plugs are. That part should be located in front of the oil pan area, right near the axle. There should be a 6 pin connector attached to your engine, it will have about 5 wires connected. The first wire should be a pink and black wire, with three more wires next to it. The last wire is a white wire, where the tach signal is coming from. There are two white wires. For the correct white wire, it is the last one. It should be sitting right next to an empty pin. Look at the instructions and it will tell you which wire is supposed to be connected. As for the other wires on your tach, the red and black one are obviously the power, red from the battery and the black one is to ground. It would be best if you connect it to metal under your dash board or to any wire you have connected to ground. For the remaining wire, you would have to connect that to your dimmer, so it dims with your dimmer switch. If you need more help and detailed instructions on where everything is located, send me an e-mail and I'll be glad to help you out.
Peace