Adding another language is fairly simple process. In order to add another language you have to edit settings.php file located in /settings/settings.php. To you is important two variables: 'locale'=> 'en_EN',
'available_locales' => array('en_EN','lt_LT')


Locale variable defines default application language. And available_locales defines what languages site supports. In order to access application another language you have just append locale before all the rest url. Then working with application you no need to worry about languages url it's appended automatically.