xx9gt6xx

Okay guys I just purchased the Auto Meter DPSS Gauge (Digital Tach + Shift Light, etc.) and I do not know where to hook up the signal wire to get the RPM reading. Does anyone know?? It says connect to the negative terminal of a standard ignition coil, or "Tach Output" terminal on the Electronic Ignition Module (Which I don't have). I have a Haynes manual but I couldn't pin point a spot to tap into. Help me out guys!