Debian (.deb) packages are the packages that are used in Ubuntu. You can install any .deb package in your system. .deb files can generally be installed from your file manager (Nautilus) merely by clicking on them, since file associations with the default installer is already set in Ubuntu. These instructions are for those who wish to install packages from the command-line terminal (Terminal).
To install a downloaded Debian (Ubuntu) package (.deb): Open Terminal and type
sudo dpkg -i packagename.deb
To remove a Debian (Ubuntu) package (.deb):
sudo dpkg -r packagename
To Reconfigure/Repair an installed Debian (Ubuntu) package (.deb):
sudo dpkg-reconfigure packagename