Help installing shift light..

Hi.. I've got an Autometer Pro Lite shift light thats been sitting in my room for about 8 months, and I'm thinking its about time I get it out of the way and into my car..

Problem is, I don't know where I should connect the wire to get a tach signal.. Is there a wire on the back of the guage cluster that I can use, or do I have to run a wire into the engine bay? If I do that, where do I hook it to? I have what seems like 100 wires added under the hood for my swap, so its really confusing in there..

Anyone have any experience with these lights?
Thanks...

theres a tach wire in the gage cluster its blue, test it