OK, this must be something really obvious that I'm not seeing but...

how do you access the CivIII editor? I can't find it anywhere.

You have to open the .bic file included in order to make changes via the editor. Hope this helps. :)

Or go to "Start" --> "Programs"--> "Infogrames Interactive" --> "Civilization III" --> "Civ3Edit" --> "Civ3Edit"