To install important updates such as security and recommended patches, you can use a tool included in Ubuntu. Start by clicking on the first icon on the top left of your screen and then type software updater.

Keep in mind that Ubuntu will also automatically inform you when any updates are available and you can choose at that point if you want to install or not. The System Updater also informs you when a new version (ie: old version is 14.04 and new version is 16.04) can be downloaded and installed.