To reset your Apple Watch when you've forgotten the passcode, follow these steps:

• Ensure your Apple Watch is charged and connected to its charger.
• On your paired iPhone, open the Apple Watch app.
• Go to the "My Watch" tab, tap on your watch at the top, and then select "All Watches" at the bottom.
• Tap the small info (i) icon next to the watch you want to reset.
• Tap "Unpair Apple Watch." Confirm your choice by entering your Apple ID password when prompted.
• Your iPhone will create a backup of your Apple Watch, and the watch will be unpaired.
• Follow the on-screen instructions to set up your Apple Watch again.

This process erases all data on the watch, but you can restore from a backup during the setup. If you don't have a backup, you'll lose your previous settings and data.