Help me find a 'clean switched power source'

Hi all!I have to fit some Denali D4 lights to my bike.The instruction manual (here) - tells me to wire it into 'clean switched power source' and use a 'test light' to determine this."3.3 - Tapping Switched PowerStep One: Two examples of possible switched power sources are the low beam and tail light, however there are many other possible sources in most vehicles. The simplest way to identify switched power is to use a test light to probe connectors/wires while cycling the ignition. A clean switched power source will only be live when the ignition is cycled “ON”, it should lose power when the ignition is cycled “OFF”.Step Two: Once a proper switched power source has been identified use the included Posi-Tap to tap the white trigger wire into the identified switched power source"I have a 2008 Kawasaki Versys. Anyone know how I would find the right line to tap into? And what is a 'test light'?Thanks in advance. via /r/motorcycles https://www.reddit.com/r/motorcycles/comments/8qilp2/help_me_find_a_clean_switched_power_source/?utm_source=ifttt