Gen 4, Sport, Gen 5+:
Wear the smartwatch above your wrist bone with the watch still and flat against your skin.
Assign Heart Rate to one of your watch face’s data points from the brand watch app options. Your BPM reading will automatically update every twenty minutes after the first reading, or you can prompt a reading at any time by tapping the icon. You will see dashes on your screen after tapping the heart rate icon; be patient. It can take 10-15 seconds to capture a reading. If the sensors have trouble capturing your heart rate, the smartwatch will walk you back through wear recommendations.
Take a manual reading at any time in the Google Fit watch app by tapping the heart button. Manual readings taken in Fit will appear here with time stamps. Your heart rate will automatically track during workout sessions. The stats will appear with the rest of your data in the Workout History section of the Google Fit watch app.