No, you should add them to tpa/preset/system/language
you will then need to delete the lng.lst and lng.dat files that are also in the tpa/preset/system/language directory. (the phone should rewrite these with the new languages when you restart it)
you will need to find and edit the allowed_language.txt to allow your desired languages.
eg. if you wanted to add english, you would start with a list of languages like "zs, zh," in the file, and you would just need to edit english in like so "zs, zh, en,"
Follow the link tonywong41 entered.
Hope this helps!
Remember that you DO NOT need to take out battery after made changes.
Simply unplug the cable and start the phone. You'll see the following message: Please Wait...
That indicate the phone is "updating" the files you've made changes to.
And again, I advice you to follow the link to the thread of changing languages!
Good luck my friend, let me know if this helps!