When I go to the Settings> Scenry Library I see boxes checked. In my case it's FSX and Orbx . Do I leave them all checked or just check the boxes that pertain to my next flight. Also, it gives an option to add, what's that about and how is that done?

You should only enable/disable Orbx add-on scenery via the "FTX Central" which should have a shortcut icon on your desktop. Leave the FSX add-ons alone, they require no real fiddling.

 

The add/delete area menu selections will only come into use when you add new aftermarket scenery (again Orbx does it as part of the installation process and only turn the Orbx sceneries on/off in the FTX Central window). I think there might be some more commentary in the Learning Center of your FSX basic program about handling the Scenery Library settings.