A phone boaster? What's that, something that brags about your shiny new smartphone?

Heh, I get it, a signal booster. Good luck with that, most rarely work as well as you'd hope.

But to the question, you get to that area by popping out the chartplotter. I've posted about it here before, use the 'search' to find more. Basically you pop off the trim, unscrew the plotter and tilt it out toward you (my other posts go into much more detail). From there you can reach behind to get everything at the helm. I likewise discuss how wires run in that area (there's a hole in the starboard gunwale under there).

If you don't have the feature, there's a breaker down in the main breaker panel labelled 'Overboard Discharge'. That normally controls the macerator pump for emptying your toilet tank overboard. I'd bet most boats don't have that feature. I wired my wifi gear into that breaker. Sort of appropriate as now it controls all the wireless info going 'overboard'.