First of all, you need to create the translation file in your WordPress language.
Your WordPress language is set in your Dashboard => Settings => General

Then go to your Dashboard => Loco Translate => Plugins => LearnPress
If your language file is not created, please create your translation file by click on the “New language” text.
You need to choose your WordPress language and the location of your file. You should choose the location is System, it’s languages/plugins/learnpress-{locale}.po



Then click the button “Start translating”.