1. Open the "Settings" app on your Apple Watch. You can do this by pressing the Digital Crown to access the app grid, then tapping on the "Settings" app icon.
2. Scroll down and tap on "General."
3. Scroll down again and tap on "Reset."
4. Tap on "Erase All Content and Settings."
5. If prompted, enter your passcode.
6. Tap on "Erase All" to confirm.
Your Apple Watch will then erase all content and settings, returning it to its factory default state. This process may take several minutes to complete. Once done, your Apple Watch will restart, and you'll be prompted to set it up again as if it were brand new.