package management - How do I add a software source?

Sometimes I see sites offering Ubuntu packages via something like

Add this line to your software sources: deb http:// something something

How can I add these to my package manager so I can install the software and keep it up to date? I'd like both GUI and command line options.

You can easily add them in the Software Center->Edit->Software Sources->Other Sources->Add"

1. Start the Software Center.




2. In the panel go to Edit and select Software Sources.

   
   

   




3. In the tab Other Sources click on the Add button at the bottom.

   
   

   




4. Add the deb URL in the APT Line input field and hit Add Source.

   
   

   

Once you close the Software Sources window your cache is going to be updated automatically.

You can now browse the newly added source in the New Source sub-list using the upper left list in Get Software.