How to turn ON Samsung Galaxy S4 LED lights to use as a torch light?
Go to your apps, then select the Widgets tab at the top. Find the widget called Assistive light, and then add it to one of your home screen.
Now you can switch the camera led lights on and off by tapping on the widget and use as a torch/flashlight.
There’s no need to download apps to do this (unless your smartphone did not come with Assistive light widget).