To set up a translation project using .properties files, follow the steps below.
1. Create translation project
Login to your account, create a new translation project and add your software's source language to it.
2. Import Java properties file
Use the Options Menu in the project page to import your properties file, with translations in the language you created.
This language will automatically be set as your project's Default Reference Language after you import the translations. You can change the DRL in Project Settings.
4. Start localization
Add to the project the languages you want to localize the software into and invite contributors to translate the strings. There are also other translation options you can choose from.
At any point during the Java localization process, you can export the language files, using the the Export function in the Language page.
Note: If you want to automate the import/export steps of the localization process, consider using the POEditor API or one of the integrations with code hosting platforms.