Listify is translated in to many different languages! If your language has translated 75% or more of the strings in Listify the language files will automatically be packaged with Listify. This means if you have WordPress set to use your language they will be applied automatically.
If your language is still not being applied, you may need to rename the language files depending on your locale. For example, by default the French translation ships as simply
fr.po. WordPress requires a country code and locale for language files so if you simply need pure French, you can rename them to