If a translation file for your language does not come bundled with this plugin, then check out this URL:
http://codex.wordpress.org/Translating_WordPress

It will walk you through how to translate the plugin using the provided template file, "tabbed-login.pot".

Once you're done and have the plugin translated, please send me your translation file so that I can bundle it with my plugin.
Send me traslated files at: vivek.marakana@gmail.com

I will give you credit and it will help others who speak your language.

Thanks,
Vivek Marakana