Dave is correct that it should lead to an AC master on and off switch. If that was the case you would see a panel and what ever panel is installed, make sure it has the reverse polarity light on it. (I use to tell my customers if that reverse polarity light ever came on to unhook and get away from the dock as I use to say reverse polarity can also mean electrocution.)
In addition, any AC system on a boat should also have a GFI and I was installing those long before it came standard on shore power just for safety sake.
Anita, I am not sure where the inlet is but I would make sure what it leads to before using. If in the back, the back panel in the rear berth can be removed by removing the screws out of the wall and then pulling out. I strongly urge you do this as it could have been installed mickey mouse style. If so, please correct it to ensure your safety.
I installed too many on the 26 and 260 and know a thing or two.