To reset a Bluetooth earphone to its factory settings, you can usually follow these steps:

1. Turn off the Bluetooth earphone.
2. Press and hold the power button or a specific reset button (if available) for a few seconds until you see some indication that the reset process has started (such as a flashing light).
3. Release the button and wait for the earphone to turn off completely.
4. Turn on the earphone again and it should now be restored to its factory settings.

If the above steps do not work, you y refer to the user nual of your specific Bluetooth earphone model for detailed instructions on how to perform a factory reset.