Translation

If you want to translate the admin area of the plugin, frontend text you will need to translate the .po files within the plugin. The files are included in the languages folder and you could use software like Poedit or a plugin such as Loco translate.

Once you saved the files you need to rename them using your locale, so for example the fille could be name slotslaunch-de_DE.po and the compiled version slotslaunch-de_DE.mo.

You need to place both files in the languages folder.

Also, you can send those files to support so we can include them on the next version of the plugin and don't loose the changes on updates or if the translation it's related just to your site you could add the following code in your theme's functions.php and save your .po and .mo file in wp-content/languages/plugins/ folder:

<?php
function wpse159536_override_mofile_path( $mofile, $domain ){
  if( 'slotslaunch' == $domain ){
      $mofile = WP_LANG_DIR . '/plugins/' . basename( $mofile );
  }
      return $mofile;
}
add_filter( 'load_textdomain_mofile', 'wpse159536_override_mofile_path', 10, 2);