Numix Icon Theme is my favorite icon theme for my Linux desktop. Here I want to show you how to install Numix Icon Theme on my Xubuntu 15.10.
To install Numix Icon Theme, first add Numix PPA to Xubuntu via Terminal
sudo add-apt-repository ppa:numix/ppa
Update repository
sudo apt-get update
Install Numix Icon Theme
sudo apt-get install numix-icon-theme-circle
Now open Xubuntu Settings | Appearance
Go to Icons and select Numix icon