Near the bottom of the http://gnormalize.sourceforge.net/ page there is:
Originally Posted by Airycat
To install gnormalize, with root privilege, execute the bash script command:
tar zxvf gnormalize-version.tar.gz
So you must download it (click on the link on that page), open a terminal window (google it), then type the commands as you see them. The first extracts files out of the "gnormalize-version.tar.gz" archive. The second changes your current directory into the newly extracted one. The third run installs the software.