Jom social has a built in language pack in Spanish which you must install (can be found here). Also install the main Joomla Language pack (from here).
You can then handle the site natively in Joomla using the multilingual plugin (you will need to enable this).
Else install a component such as JoomFish (I believe the 2.5 version is only a paid membership thing for now - but a free one will probably come soon) or FaLang (free but I personally don't find as good). There are also other components available on JED which will manage the translations better than the native Joomla plugin. However the above two langauge files will need to be installed either way!