After you translate the strings, you would find the language files inside the /languages folder under the “user-private-files-pro”plugin directory. Copy the languages files to the “/wp-content/languages/plugins/” folder.
Then, if you change language from wordpress general settings, it should work directly and you would see the translated text.
If you want to use multiple languages for your site, you would need to use a multilingual plugin (e.g. Polylang) to add multiple languages to your site.