When I installed my tach, I hooked it up to a green connector that had a rubber boot over it next to the igniter/coil. I installed a flat male electrical connector on the tach wire and plugged it in. I then wrapped it in black tape to keep it from shorting out. There were three other wires coming out of the tach. One was for switched power, one was a ground, and one was for lights.
^Came from Yota Tech