“How best to track sleep with Apple Watch?”

If you have an apple watch

Our recommendation is to wear your watch at night and track your sleep with the Apple Watch, which syncs to Gyroscope automatically.

More importantly, it provides the resting heart rate and HRV measurements which are used by Health Score.

This can be turned on in the Watch app on your phone!

If you don't have a watch or other wearables

The sleep AI is more intended for people with no watch or any other sleep data, and in that case you can access it by opening the daily report for any day — and then it will show a suggested sleep that can be saved.