Bring the machine up to date

After updating /etc/apt/sources.list, execute the following two commands:

$ sudo apt-get update
$ sudo apt-get upgrade

This will update any packages on your system to newer versions released after the CD. The update may take quite some time, depending on the number of packages to be updated, the load on the repository servers and the speed of your internet connection.

When the update is finished, reboot your system to take advantage of a possible kernel update or new system packages.