This phone is compatible with Android 4.1.2 and you can update to this OS version using the OTA (Over The Air) upgrade. Go to Settings > About Device > Software Update and mark your phone to always be notified of updates. If there is an update, it will be provided this way. Make sure to have a stable WiFi connection because the download could be a little big.
Another way to upgrade is trough the official Samsung application. Download Samsung Kies and install it, then connect the phone and wait for drivers installation. If there is a new firmware available, you will be notified about it.