There are 2 ways to use the LED falsh as a flashlight on Galaxy S7: add a flashlight widget to the home screen or add a torch toggle button on the notification panel. to enable flashlight on Galaxy S7 and Galaxy S7 Edge, do as follows:
Add a flashlight widget to the home screen:
1. Press the home button to go to the home screen
2. Press and hold you finger on a empty spot on the home screen to enable the Home edit mode
3. Touch the Widgets icon to see the list of available widgets on your S7
4. Browse through the widgets, and find the Torch widget (It' sorted alphabetically)
5. Now, simply drag and drop the Torch widget on the home screen
6. To turn on the flashlight on Galaxy S7, tap the Torch widget.
Add the Torch toggle button on the notification panel:
1. Drag down the status bar to open the notification panel
2. Drag down again to view the complete list of system shortcuts
3. Hit the Edit button and there you should see all the toggle buttons (both actives and in-actives)
4. Find the Torch button and drag it a suitable spot
5. From now on, to turn on flashlight on Galaxy S7, you just need to pull down the status bar and touch the Torch button