Download the tar.gz file and extract it. In the new folder created, run the ./INSTALL script to choose the distribution logo (Ubuntu, by default) and the Gnome menu icon. If run as root, the script will copy the iconsets to /usr/share/icons to made them available to all users. Some default icons used by Rhythmbox and Dockmanager may be also replaced.
Run ./UNINSTALL as root to restore defaults icons.
Faenza icon theme is available to install for Ubuntu users via a PPA repository. View the README file for instructions and a list of known issues.