Go at http://ftp.gnu.org/gnu/gnuzilla/ and download the latest package.
Extract it at your desired location.
There, you may be able to launch the browser by just double clicking the
icecat executable, or try first, by opening a terminal in that location:
chmod +x icecat
To create a desktop file like for a normally installed browser:
gedit text editor:
sudo gedit /usr/share/applications/icecat.desktop
Then paste this, changing accordingly the lines that start with
Name=Icecat Web Browser
Save, close, and you should see it in Dash or other launchers, or add it to a panel etc.
Depending on your desktop environment and/or launcher: in order to properly see the icon in the launcher,
icecat.png file might be needed in a proper location.
Let's say we have a 128x128 file called
icecat.png (that we can get from somewhere like here).
Go to the location
~/.local/share/icons/hicolor/128x128/apps/icecat.png ( or create it first), and then again
sudo gedit /usr/share/applications/icecat.desktop, change the necessary line to