If you are using Linux or macOS: open about:config and set ui.context_menus.after_mouseup to true. Otherwise, the context menu will show up before the extension can detect the gesture. To make a gesture, hold the right mouse button, move the mouse and release the button. Gestures:

• Down: open a new tab
• Down → Right: close the tab
• Down → Up: duplicate the tab
• Left: go to previous page
• Right: go to next page
• Up → Down: reload the page
• Up: stop page loading

The extension doesn't work on restricted pages like addons.mozilla.org