An easy way to check, just to be sure, is to get a volt meter (the kind with the individual probs). Put the black lead in the neutral slot of the plug and the red lead in the hot slot and it should read zero volts. Fire up the generator and check again. It should read around 120v. It really does not matter which slot either lead goes.. If it's reversed, it'll just show -120v. Swap them and it'll show +120v and you'll then know which is which! :)
Plug in the male end and you should now have power to your 120v plugs and appliances in the RV.
I've never seen one wired up in a single box that way, but you can tell there are 2 separate wires going "in" and the single plug going "out".
Have fun finding out about the LP powered appliances next! They are probably pilot light operated and those take some extra, manual steps to lite! ;)
Mitch