hi Jaycee, if you are wanting to install another country which is not in the NEK Redux pack, you will need to add the country to a number of files. You can add a character to the character folder if you want, otherwise reference an existing pilot model in the country.xml and unlimitedpilots.
Add a country (using a three letter name) to the uires folder, together with images for flag etc. You can poach images from another country in the uires if you like.
Add a country (with all the airbases in the GL) to the cutscenes.xml, a mention of the new country in the pilotconstants.xml, addition of the new country to the file assigned to single missions in the game.xml (for example the file for ETO is NEK_ETO.xml in the campaigns folder), and the biggie is the relevant bits in the country.xml. The three latter acronym is need in the country.xml as well as the uires. Add a pilot to the unlimitedpilots.xml found in the root pathway for the install (not the appdata pathway).
I don't have a version of CFS3 in front of me so I may have missed something. It looks fiddly but just looking at how it has been done for example in ETO, makes it fairly easy to follow.
If you don't add a set of vehicles for the country, sometimes facilities will spawn which are empty of vehicles because CFS3 assigns nationalities to facilities at random (unlike air spawns). There may be a much better and fuller explanation in the readmes for NEK.