It is important to have the system updated, so that we have all the latest patches, security fixes and packages upgrades from the repositories.

First, navigate to: System –> Administration –> Software Sources

and check that all repositories are enabled.

Then, open the terminal: Applications –> Accessories –> Terminal
and type: (you need to provide the password here)
sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade

With this you are done with the system update.