How do I add to "system software sources"?
7371
What are PPAs and how do I use them?
101278
How can I add an application to the list of Open With applications?
70860
Adding default package imports
53183
What's in "standard system utilities" in the server install?
19565
Restore default apt repositories in sources.list from command line
28712
How can I add screenshots of programs to the Software Center
4778
Install software from packages, or build it from source?
71959
Is there any simple way to access installed programs?
19175
Adding a systemd .service (Debian)
137126
How Do I Allow A Standard User to Install Programs?
150069
How do I install wunderlist?
115687
How do I properly install a system app given its .apk?
18829
How to add programs to the Unity Launcher or Ubuntu Dock?
138386
Can I install items on Ubuntu, without using the command line?
115896
How can I install the $0 applications from the Ubuntu Software Center with apt-get?
24021
How do I install .run files?
51515
Where can I find the source code of Ubuntu?