I just installed mine and it was pretty easy.
Black is the ground. just attach it\screw it to any metal part of the body.
The tach wire (color varies to tach) will attach to the tach wire coming from your dash gauge. It should be a light blue wire. Just tap into that.
Red positive wire will need to be powered only when the key is on the on position. So look at your ignition(where you put your key in) There will be a thick yellow wire. Tap into that wire. The white wire or in-dash lighting wire, i dunno where to wire that, so i just wired it into that yellow wire also.

Have fun.