On many forums Ubuntu users still struggle to install .deb files manually. The .deb file is actually a package.
The packages which you want to install manually, have to be installed via the dpkg command (Debian Package Management System). Basically dpkg are some backend commands like apt-get and aptitude.
The easiest way to install a package of course is through the Graphical User Interface, through the Synaptic or Software Center. As an alternative you can install package by terminal commands like apt-get and aptitude that have a friendly approach to the backed dpkg. But still not limited to have a control on all packages, like which one needs to be updated, which one is broken, etc…
So, as you understand now, the dpkg is the base, and it allows you to install packages with no problems from the command line.
To Install a .deb File Package
You will have to open the terminal using the keyboard shortcut: Ctrl + Alt + T and type the following command:
sudo dpkg -i DEB_PACKAGE_FILE
Note that DEB_PACKAGE_FILE should be replaced with your .deb file. Also you will have to indicate the source directory of the file.
If dpkg reports an error due to dependency problems. You can run the following command:
sudo apt-get install -f
This command will download and install the missing dependencies.
To Remove a Package
To remove a package use the following command:
sudo dpkg -r PACKAGE_NAME
For more information about how to remove a Package from Ubuntu using the terminal commands visit this page.