BOSS bv6654b

Hello! We recently purchased a 2016 Heartland Trail Runner SLE with a Boss bv6654b stereo/DVD player. The problem is we cannot figure out how to turn it on. Any ideas?
Absolutely nothing. There is a switch above the sink that so far doesn't have a purpose. Heartland says may be connected to the stereo, but still no power no matter what position it's in.