Ah I see what you mean now.
My LEDS/HALOS are wired to a seperate switch instead of my parking lights. So I can turn them on whenever I Want. I like to leave them on when I head into stores ha
Best thing to figure that out is to put your parking lights on (Selector switch) and take a voltmeter out. Get on your neutral (-) than find your positive(+) with the steady 12V. Its pretty simple, well if you have experience with DC electrical circuits and a meter of course.
Even if you want to isolate it better. leave all your lights off and shove your hazards on (or turn signal your choice) and than apply your voltmeter to your neutral (-) and your Positive (+) (it might be to fast to read) you will see it fluctuating on/off/on/off. You get the idea you DONT want to slice onto that wire
Here's my thread on my Switches for my halos/leds also