In order to activate a language in eFrontPro, log in as administrator and from your Administration dashboard navigate to languages. Over there you will be able to view all available languages in a tabular list.
To activate a language use the toogle operation to activate it (1). Inactive languages will appear in the list with red color.
Once you have activated a language it will be available in your language options (2) for the user languages or the system default language.