Installation very simple with few components:
-Zener diode 5.1V
-Capacitor 470µf 10V
-Heat Shrink Tubing
Solder the components on the pcb and before to shrunk the heat shrink tubing, do a test with the battery.
The capacitor allow to had a smooth light off.
Step 2: Mod Your Cordless Driller
Mod the case for add the LED.
Place the circuit.
The positive must be solder to the battery socket positive (blue wire). The Negative must be solder to the Mosfet (Source - pin3)