Ubuntu recently announced and released a new version of their operating system, called Wily Werewolf. This is version 15.10 of this Linux distribution and is officially supported until 07-2016.
To upgrade your Ubuntu installation to the newest Ubuntu 15.10 release, open terminal and execute the following command:
sudo do-release-upgrade
Upgrading Ubuntu from the command line is really that simple.
Obviously, it’s always recommended to make a backup of essential files/folders. Furthermore, this is not a LTS (long-term-support) release, so you might want to wait for such a release to upgrade your installation of Ubuntu.