There are four methods of updating / upgrading your Android OS
Automatic (update notification) method
Update search method
Manual method
Using custom ROM
The Automatic (update notification) method of updating Android OS
Upgrading the Android OS on your smartphone / tablet via this method is easy. This is because your carrier automatically sends you the latest updates so sooner or later you’ll get an over the air (OTA) update to the latest supported Android OS. All you will need to do is confirm the installation and let it go. Ensure you have a sufficient data plan (See: How to control heavy Android data / MB consumption). Once installed, you can confirm by going to your phone’s device information screen to see that the latest version of Android is now on the phone. On some Samsung devices, you’ll need to enable your Samsung account in order to upgrade Android OS. To do so:
Go to Settings
Select Accounts & Sync
Select Add account
Select Samsung Account
You will then be prompted to set up a Samsung account, which requires inputting your email and creating a password.
Source: http://blog.hovatek.com/how-to-upgrade-an-android-smartphone-or-tablet-operating-system-os/
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