http://www.t3-framework.org/documentation/bs3-customization#multiple-language
but new t3, have some step have different
Step 4: Assign menu for Megamenu
–> just change MENU , change to your wnat language, then can use.
http://www.kenming.idv.tw/web-building_config_multi-lang_site_with_joomla25
http://help.joomla.org/files/EN-GB_multilang_tutorial.pdf
Use
Components -> JA Extension manager
check update ~ ~