Press the Superkey (Windows key) to launch the Dash and search for Update Manager
Check for updates
Click the Check button to check for new updates. If there are any updates to install, use the Install Updates button to install them, press Check again after that first update is complete — then press the Upgrade button.
Install the upgrade
A message will appear informing you of the availability of the new release. Click Upgrade and follow the on-screen instructions.
Download Ubuntu for desktop
To download and install Ubuntu, all you need is a blank DVD or USB stick.