LED Glow Under Dash/Under seat kit

I'm sure this gets posted so many times here. This is I believe my second post here.

I am very interested in redoing all of the lights in my 2015 Cruze LTZ RS, it is Red so I would like the lighting inside to be Red, the dome lights I can handle (I decided to keep the map lights white but switch them to LED because I am sure reading anything in red light would be a pain) however it is the accent lighting that I am both extremely excited for and nervous about all at the same time. LED Glow has some awesome deals on some kits that do multiple colors though red is really all that matters to me. My only stipulations are that I want them only to come on when my dash lights come on and also to be dimmable with the dash lights. The problem with that is I have no idea where to splice the wires. I am confident that with a little guidance I'd be able to do it... it's just knowing where to go... and I couldn't think of a better place to start!

Any help would be greatly appreciated.

Thank you