Download and extract (if needed).
Create a folder with the name “.icons” in your home folder for all NON-KDE/PLASMA desktops.
Create a folder with the name  “icons” folder in your home folder ~/.local/share folder for KDE/PLASMA.
Move the icon folders inside the newly created folder.
Now select it with the tools provided by your desktop. 

Download Sardi icons

Download Surfn icons