Ubuntu installation notes for clamtk-gnome add-on
Typically you can just doubleclick the .deb to install it. Just in case you want or need to do it by commandline, here are some quick instructions:
First, install the .deb:
sudo dpkg -i clamtk-gnome_0.01-1_all.deb
If you see installation errors (e.g., missing dependencies such as python-nautilus), do this:
sudo apt-get install -f
Note that you may have to log out and log back in for the context menu goodness.