Translation - choosing a language with OJS


I understand that there are various language packages that can be used to translate textual material into a different language. That said, I am investigating the use of OJS software for a journal that has, until now been fully bilingual (English and Canadian French). Does the OJS software allow you to switch back and forth between translations, or do we have to have two fully independent instances of the journal and users would set their own preferences? Is there a method, using custom programming, of moving between translations that could be added (I am not a programmer)? Thank-you