The best way to update to Android Lollipop is with the help of the dedicated software provided by Samsung or through the OTA. In both cases, you should make sure the battery is to 85 % or more. To use the dedicated software, simply download Kies from the Samsung support website and then connect the phone. Let Kies update the necessary modules, and click YES when it prompts you to update the phone. The second method uses, Over The Air procedure to download the update on your phone. It can be triggered while you're connected to a network. Go to Settings > About phone > Software Update and follow the procedure. You might need to create a Samsung account in order to properly download the update.