http://askubuntu.com/questions/14629/how-do-i-enable-the-partner-repository
GUI Way:
Click on the ubuntu button, then search for "Software Sources" and go to the "Other Software" tab.

Command Line Way:
- Open the sources.list file:
gksudo gedit /etc/apt/sources.list -
Add the partner repositories by removing the # in front of the following lines (
maverickis the version of your Ubuntu installation, it may differ)# deb http://archive.canonical.com/ubuntu maverick partner # deb-src http://archive.canonical.com/ubuntu maverick partner

- Save and Close.
-
Resynchronize the package index files from their sources:
sudo apt-get update -
Official documentation (https://help.ubuntu.com/community/Repositories/Ubuntu#Adding%20Canonical%20Partner%20Repositories)for reference