Hi,
mojoPortal is not really designed for multiple languages in the same site. Label and buttons will already automatically adjust to the user language setting as specified in browser settings. But there is no translation of content in the database so I recommend you create a different site for each language and link them together with flag icons like I have in the top corner of this site. Then have authors in each site that create content for the language of the site. You can even share users across the sites if they are running in the same installation and using related sites mode.
Hope it helps,
Joe