After installing Lumos via Cydia on your device, you'll notice a new icon on the lock screen, allowing you to quickly activate the device's flash. To turn on the flashlight, simply tap on the flash icon.
Tapping the icon once more will help you turn off the flashlight.
Navigate to the tweak's utility panel from the Settings app to configure its settings.
You'll see two types of icons available for selection, and you can even adjust the position of the flash icon on the lock screen by configuring the 'X' and 'Y' sliders. The 'X' slider sets the horizontal position, and the 'Y' slider sets the vertical position.
You can also tap on the numbers next to the slider to manually adjust values from 1 to 100.
https://Mytour.vn/quickly-enable-flashlight-from-lock-screen-on-iphone-ipad-844n.aspx
If you frequently use the flashlight on your iOS device, you should check out Lumos. The Lumos tweak is currently widely available for free on the BigBoss repository of Cydia.
