Charging system

Follow the instructions that should have come with the charge light. Or, if it has black and red wires from it, just connect them to any positive and negative feed in the headlamp shell.   

In theory RED/BLK to Positive and Negative in headlamp 'sounds correct' BUT what year Dommie? Magnetor/Dynamo or coil? What charge light? The BSM I sell comes with instructions and needs an ignition switch.
The 'red light out' which is fitted to Commando can be used but extra wiring as with the unit I sell.
Any unit you buy needs to come with instructions, if not reject it. Not fit for purpose!