To remove the previous owner from your Apple Watch, follow these steps:
1. Open the Settings app on your Apple Watch.
2. Go to General > Reset.
3. Tap "Erase All Content and Settings."
4. Enter your passcode when prompted.
5. If you have a cellular plan, you'll be asked to choose between "Erase All" and "Erase All & Keep Plan." Select "Erase All" to completely remove the previous owner.
6. Wait for the process to finish, and your Apple Watch will be restored to factory settings.
Please note that this will erase all data and settings on your Apple Watch, so make sure to back up any important information beforehand.