Installing gauges

[Zondo956]

2016 t680
I’m trying to install a pyro gauge and haven’t been successful.
Can I tap Power, ground and ignition into radio?

I’ve found the wires needed for that but can’t find where to get power for lights. I thought it would be easy to tap into a wire behind the light switch. When checking for power with a test light I couldn’t figure out how the switch works and the illumination light burnt out for headlight switch. Gave up on that idea.
I’ve seen Rawze video on install but my fuse box is different.
How have others wired their gauges?