For this, please follow below steps:
Create new directory wpsp in wp-content/languages directory.
Make sure you are using correct text-domain and locale for your .mo file.
text-domain for this plugin is wp-support-plus-responsive-ticket-system
your locale should be same as your your WordPress installation language locale.
e.g. If you are translating for French language locale must be fr_FR
So in this case, translation file name should be wp-support-plus-responsive-ticket-system-fr_FR.mo
Now upload your translation file (.mo) to wp-content/languages/wpsp directory
Done! Now you will see text in your translated language for WP Support Plus