How to use double tap to turn off the screen?

If you want to use the double tap to turn off the screen function, please refer to the following steps:
1. Open [Settings];
2. Click [Lock screen];
3. Turn on [Double tap to wake or turn off screen when device is locked].
Note:
1. The double tap to turn off screen function is only available when the screen is locked;
2. You can double tap to turn the screen off only when using either the "Classic" or "Limitless" theme.