You can only update your OS version to a newer one only if the developer has released an update that is available for your device. To check for updates and install them you can try going to Settings -> Privacy -> and check Back up my data. After this, go to Settings -> About -> Software update -> Update. This will automatically search and download for possible updates available for your device. In order to do this, first you got to connect your device to the Internet, preferably using a WiFi connection.