How to install DEB file on Ubuntu
A Using graphical interface (GUI)
For desktop users, the easiest way is to install using GUI. Simply right click the file and select Open with Ubuntu Software Center. Then, Ubuntu Software Center will display additional information corresponding to the DEB file you've selected. Press Install to start install the DEB file.
B. Via Command Line (Terminal)
For some advanced users, they sometimes prefer to use command line interface in order to perform some administrative tasks such as package installation. Use this command to install DEB package onto the Ubuntu System.
sudo dpkg -i packagename.deb
where packagename is the actual name of a deb package. Simple right? Keep the learning spirits.