Repositories are the thousands of Ubuntu programs available online for the needs of Ubuntu users. Many of these programs are stored in software archives which are commonly referred to as repositories.
Enable Universe Repository from Ubuntu Software Center
1. To enable the so called “Universe” repository, which is a community maintained repository and its free and open-source software, you will have to open Ubuntu Software Center. You can find it from the Unity menu by typing in search ‘Ubuntu Software Center’.
Then up on the menu bar click on ‘edit‘ and then ‘software sources‘.
2. From ‘Software Sources’ you can check to add the: “Community-maintained free and open-source software (universe).”
Enable Universe Repository from the Terminal
Open the terminal, and start by adding the universe repository:
sudo add-apt-repository universe
On older versions of Ubuntu, you might have to use a full source line:
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu $(lsb_release -sc) universe"
To enable all Ubuntu software (main universe restricted multiverse) repositories:
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu $(lsb_release -sc) main universe restricted multiverse"
After adding the repositories you will have to update the package list with the command:
sudo apt-get update
Tha’s all. Hope everything worked fine.