e-Newsletter language settings

Dear,

Let me first say, what a great plugin is e-Newsletter.

However, I am struggling to understand how adding another or simple replacing the existing language works. I could not find that info withing the plugin page.

So far, I believe to understand the part about how to edit exiting translation file with Poedit software but then, after I create my own language translation (french) I am not sure if these file should be in the same directory as default language or a sub-directory named fr or french, should the file be named by default or french.po etc...

Please advise.

Thanks for a great support as always!

Regards