In order to be able to use Ubuntu Software Centre from behind a proxy, you need to jump through a few hoops:
Click the search button (top button on the left side), and in the search box at the top type
In the Terminal type:
sudo pico /etc/apt/apt.conf
when prompted, type your password
add the following 3 lines:
Acquire::http::Proxy "http://comp101:firstname.lastname@example.org:8080"; Acquire::https::Proxy "https://comp101:email@example.com:8080"; Acquire::socks::Proxy "socks://comp101:firstname.lastname@example.org:8080";
and now you can run the Ubuntu Software Centre
and what does it all mean?
Terminal is the Program that gives you command line access to the computer.
Sudo gives you root (superuser) access to the machine.
Pico is a text editor
/etc/apt/apt.conf is the configuration file for APT, the Advanced Packaging Tool
the 3 lines in that file are of the format: Acquire::http::Proxy”http://user:password@proxy:port”
for the 3 types of proxy: http, https & socks