First download the alternate language prompts from the asterisk website. If your language is not available it might be found from a 3rd party website. If unsure which type to choose select gsm.
http://downloads.asterisk.org/pub/telephony/sounds/releases/
create a directory in /var/lib/asterisk/sounds and copy/unzip/untar the sound files into it.
Set the ownership of the directory (which we called "somedirectory" in this example) and files for asterisk use:
chown -R asterisk. /var/lib/asterisk/sounds/somedirectory
Go into FreePBX GUI>Settings>Asterisk SIP settings>Language and enter the name of the directory which in this example would besomedirectory.
After you save and apply changes you will now have alternate language voice prompts.
