On the iPhone X and later models to quickly turn the torch on or off swipe down from the top right corner, this opens the control center which has the flashlight button. Tap on the flashlight button to turn it on or off. The icon will turn blue when the flashlight is on and white when it’s switched off. The brightness of the flashlight can also be adjusted manually. To do this, press and hold the flashlight button in Control Center and drag the brightness slider up or down.