Unfortunately, Android OS v4.2.2 is the latest version released for this phone. To check for other updates, go to Settings > About phone > Software Update. Connect to a WiFi network and make sure the phone is charged to at least 85 %. This is the only way to check for available updates. Android KitKat 4.4.4 might come in the future for your phone but unless is announced officially, you need to use the version you already have.