To sync your Garmin data with Athletica, ensure your fitness tracker shares data with Apple Health. Follow these steps: 1. Install Garmin Connect from the App Store and sign in. 2. In Garmin Connect, go to More > Settings > Connect Apps > Apple Health. Select "Connect with Apple Health" and allow access. 3. In Apple Health, go to Summary > Profile > Apps and Services > Connect app. Toggle categories as needed.