It depends much on where and how the strings are used.
In the menus, translation is easy, since they are mostly referred as @STRINGFILENAME_REFERENCE.
In the ingame (ICARUS scripted) cutscenes, it depends if the subtitle was simply entered as string (such an "error" we did in our mod),
or if there was also a reference used.
Simply add a directory with your language in strings, e.g. strings\italian,
and add the translated files there.
JA requires at least SP_INGAME.STR and MENUS.STR to be translated.
If either file is missing, JA will either display an error, the english original text, or simply nothing.
In MENUS.STR you have to modify the one string that designated the language:
And remember: always keep the reference and the english string inside:
LANG_ENGLISH "This is my first own string"