To use the Garmin Rally XC200 power meter pedals, first make sure your pedals are compatible with your Shimano SPD cleats. Install the pedals on your bike as you would with normal pedals. Once installed, pair the pedals with a compatible device. When you start riding, the pedals will start measuring your total power, cadence, and left/right balance. You can see the accurate measurements on your paired device. As for maintenance, keep the pedals clean after each ride. Wipe them down to remove dirt and debris. Check the cleat compatibility regularly to ensure a smooth connection. Also, store the pedals in a dry place when not in use to prevent damage.