When a manufacturer makes an update available, it is either available as a manual update via PC or as an OTA (over-the-air) release. In the process of OTA, you can download the update via the data connection directly to phone, and install it without the need of a PC.
Below is how update an Android OS via OTA.
1. Tap ‘Menu’ on your phone, and go to ‘Settings’.
2. Scroll down and tap ‘About Phone’ or ‘About Android’ or ‘About’
3. Now select ‘System Updates’ or ‘Check for updates’ (this varies from phone to phone).
4. If there is any update available as an OTA download, you will be notified. Press ‘Install It’. It will be downloaded and your phone will be restarted automatically. However, this will incur data charges.
1. Make a backup of your contacts, messages, apps, and whatever you can. There are lots of apps available on Google play for helping you in this scenario. See this post for more info.
2. Also, make sure that your phone has a charge of above 50 percent to sustain the upgradation process. You won’t like to see your phone getting switched off in-between the update process.