The Sardi icon collection is hosted on Sourceforge. You can download and install it from there.
A tutorial has been made as part of the playlist “Linux Mint 18 Cinnamon a complete customisation with Sardi icons“.
In this movie you will download the zip file, extract it and copy/paste the contents in the hidden folder .icons.
Or you should create the hidden folder .icons if you do not have it yet.
You can also use a script to get the latest Sardi icon set. That script is called “sardi-icons-latest.sh” on github https://github.com/erikdubois/Ultimate-Linux-Mint-18-Cinnamon but only if you like to use scripts. It is not necessary to do so to have the sardi icons. You can run it whenever you feel like it and it will get the latest icons from sourceforge and put them in your hidden .icons folder.
I have been making so many scripts to change the icons from colour that as a result I have a lot of working icon themes. Furthermore I have been testing to mix other icon themes with Sardi (see articles on this website) and more icon experiments. All of these files are now kept at https://github.com/erikdubois/Sardi-Extra.
Here is a tutorial how I personally install all the Sardi icon themes and the Sardi Extra icon themes.
I promised myself to show also movies in other distro’s than Linux Mint 18 Cinnamon but this does not change a thing.
Scripts will work on any linux distro.