Create a new PREFIX_gamefile.txt and replace all regular filenames with the ones of the files you added yourself.
So if you only changed Units.txt, create copy of gamefile.txt and call it e.g. TUR_gamefile.txt. Then open the file and replace Units.txt with TUR_Units.txt.
You must add three new lines to the bottom of your XXX_gamefile.txt as well. I don't have access to an example right now but just look at cradle or anything and it'll be obvious. The lines are the title of the mod, and the names of your versions of newsprite.txt and great_library.txt (but I can't recall in which order...)