You should title your post "white wire light" or somesuch.
It is easy to go overboard. Any light that's too powerful, in other words, that you could actually see by, will kill the motor. This is perhaps the conundrum that is confusing; people continue to have "bright ideas" to cheat the system but they're just, IMO, focusing a weak beam differently.
What exactly is confusing? Volts/amps/watts, how the wiring goes?
We'd like to help but your questioning is not the best.
By far the easiest thing is to find a self-grounding light from a car, motorcycle, or bike dynamo headlight. It too will have one wire. connect that wire to the white wire, with a switch in the middle if that pleases you. Done.