Open the Health app and tap the Summary tab. Tap your profile picture in the upper-right corner. Under Privacy, tap Apps. You can see apps that you already own that are compatible with Health. If you don't see an app, it might not be compatible. Tap an app and turn on the health categories that you want that app to track.

If you're using multiple apps to track different things, the Health app can keep it all in one place. Manage the data that's added to Health app.

Apple Watch apps can also read and write Health data. You can manage them directly on your Apple Watch: Go to Settings > Health > Apps.