If your only fitting a shift light and not one attached to a tacho then its even easier than that ^.
The light will have 3 wires, GROUND, RPM Signal & POWER
The only wire you need to find on your car is the RPM signal going into the OEM tacho. Which iirc is a yellow wire but id check that lol.
So power is 12v + which you can get from the fuse box, ground is to any bare metal or an exisiting ground point under the bonnet and the RPM signal from the tacho or even crank sensor.