I tied it in under the seat where the aux plug is.
You don't have to splice on a 2015 RGS all you need is HD pn 69201109. It plugs both led fogs into either left or right turn signal connector and has a female connector to plug the turn signal into. That is only if you have the fog light aux switch on the dash.I have the OEM lighted fog light switch. It didn't make a difference on my 2015. I still had to splice it together.