Do you mean factory or aftermarket?...Can't help you with factory but aftermarket is very simple...Normally you have a red wire that needs to go to a switched 12 volt source..One black wire that goes to a ground..One white wire that goes to your interior lights or can be hooked in with the red wire if you want the light on any time the key is turned on...And one green wire that you hook to the negative side of your coil....The tach can easily be mounted to your steering column with a big hose clamp....Most tachs have an internal switch that needs to be set for your engine size (4-6-8 cylinder)..

______________________________________

1968 mustang..408 windsor.Vic jr heads and intake.Pro Systems 950HP holley, 1 3/4 hooker super comps,Custom CI solid roller camshaft,Probe shaft rockers, 4 speed with 4:11 detroit locker.