Help With Wiring A B&m Trans Temp Gauge.

[Zebvance]

I am hooking up a B&M Trans temp gauge and a after market trans cooler.

 

It says to hook up one wire to illumination/ dashboard lights but I have not Idea which wire to splice into. Also It says to run one wire to the ignition wire, once again I have no idea where this is located. Sow help would be greatly appreciated!

 

The vehicle is a 1988 Comanche 4.0 4x4 auto shortbed.

 

Below is a picture of the wiring diagram.