Getting Started: Adding Languages
Unlike myAlpha, in Marriage Builder you need to enable a Language on your site to make the Translated Resource available.
To do this go to Settings -> Languages
From the Picklist choose the languages you want available. Click 'Add' and then 'Save' to add them to your site.
Currently there is a BUG where all Languages are public, however once fixed, only Public languages will be shown in the site language selector.