Using this Braun ET66 calculator is a breeze. Just press the colorful Skittles - like buttons to input numbers and perform calculations. When you're done, you can slide it into the included case for protection. As for maintenance, keep it in a dry place and avoid exposing it to extreme temperatures. Don't use abrasive materials to clean it; a soft, dry cloth will do the job. If you encounter any issues, reach out to Braun's customer service. Enjoy using this classic calculator for all your simple calculation needs!