How to Configure extra buttons on mouse I have a mouse that I bought from eBay and has two buttons on the side. For some reason, these keys don't do anything. In the modifier keys section of the keyboard settings, it called the mouse "SiliconWin mouse", I changed all the keys to command and no command worked. I thought these keys served no purpose but I later found if I pressed an application in the dock with the key, it would do the same thing as a right-click. Again I checked and tried to use the keys as right-clicks but did not work. Is it possible to change the functionality of the key?

P.S. 
I tried setting keyboard up and it asked me to press the button to the right of shift, I pressed everything and did not work.

If I search up SiliconWin, it comes up with Windows driver and no mac drivers.
If you just want the side buttons to do back/forward in ANY
  app/environment, this app is the most basic, streamlined one I've
  found for this purpose on Mac OS X, and completely free (donate!).
  http://sensible-side-buttons.archagon.net/


This answer was copied from here: https://superuser.com/a/1230059/51328