The regulator does this by sensing the RPM the alternator is turning, when it gets to a certain rpm the voltage regulator "turns on".
That's why there are numerous regulations surrounding electrical electrical wiring and installations.
The young person asking questions received positive feedback and advice from total strangers who "told it like it is" with the care many reserve for their own kids.
Have the right tools handy Such as any other DO IT YOURSELF job, you want to ensure you have the right tools to do the job.
Many systems just tap off the plus side of the ammeter to give a hot line to the light switch.