I’m not familiar with Loco Translate. I created the .po and .mo files using poedit and placed them in the /lang directory of the plugin (version 1.9.6). You should be able to use them to translate to the language you want.
In order not to lose the translation with future updates, you can place your translation files under wp-content/languages/plugins/ and they’ll be sage. Or you can send them to me to add them to the repository.