"So, you have found an application that you want to install and
use on (Ubuntu) Linux. You have searched in Add/Remove Applications
and in Synaptic, but it is not there (or there's an older version
there that just won't cut it for you). What can you do now? Have no
fear!
"...Ubuntu Tweak isn't available through the default Ubuntu
repositories. I can't find it and easily install it using
Add/Remove Applications or Synaptic. So, how do I install it?
Firstly, you download the file (this is a .deb file, which means
that it is Debian compatible. Debian is the base Linux distribution
upon which Ubuntu is built) from the website."