The default config is located at /etc/supload.conf, If it exists, it will read from ~/.config/supload/settings.conf. The home config file will take priority.
If you delete this file, it will **NOT** be recreated, you will have to recreate it.
If you are using the Gnome 3 desktop environment, you can add a custom shortcut to upload screenshots by going to Settings -> Keyboard -> View and Customize Shortcuts -> Custom Shortcuts -> In your new shortcut, entire the command 'supload -sd https://youruploaddomain.com/'