To use the Sunsynk app, download it from your app store, create an account or log in, connect to your Sunsynk inverter by scanning a QR code or entering the serial number, then monitor real-time solar system data, manage settings like switching modes or configuring charging/discharging parameters, and receive notifications about important events. Explore additional features like energy forecasting and consumption insights if available, and refer to the app's user guide or contact Sunsynk's support for assistance if needed.