> I have the .tar.gz file for it downloaded....
Don't do this..use you package manager to install software. Linux is not windows.
But in this case...why at all? Pretty much every Desktop environment comes with a gui tool for extracting files that can also handle .7z files, in plasma that would be ark, in gnome i think it's called FileRoller. No need for a gui tool for every individual package format..just use the one you most likely have already for all package formats.