Upgrade Ubuntu from one version to another.

Few simple steps:

• Go to "Software sources" change the box that "notify me when an LTS version is available" to "notify me when ANY new version is available".
• Then run your updater again, then it should come up with message "New version of Ubuntu is available".
• Click on "Upgrade button" then it will start upgrading your ubuntu. It may take several minutes, keep calm and wait for full upgrade.