Hi
Follow these steps to erase your locked Apple Watch and pair it with your new iPhone:
- Connect your watch to its charging cable, connected to power.
- Whilst keeping your Apple Watch on the charger:
- Press and hold the side button until you see the Power Off slider.
- Press firmly on Power Off (do not try to slide it - just press down more firmly than a normal tap), release and then tap on Erase all content and settings.
- Pair your watch using the Watch app on your iPhone, choosing to Restore from Backup if offered the option.
More information:
Set up your Apple Watch - Apple Support
If you forgot your Apple Watch passcode - Apple Support
For future reference, the procedure for switching your Apple Watch to a new iPhone is detailed here:
Switch your Apple Watch to a new iPhone - Apple Support
