Samsung Galaxy S6 Edge: How to Set Power Key as Screen Lock Key in Android 5.1.1 Lollipop

If you'd like to easily lock the screen without you have to wait the screen automatically turns off and the screen lock delay period ends, you can set the Power key as the screen lock key so that your phone will instantly lock the screen when you press this key. You can do this if you use one of the screen lock types with the security lock feature, e.g., pattern, direction lock, PIN, password, or fingerprints.

How to set Power key as the screen lock key?
You can do so by using the following steps:

1. While the screen is unlocked, swipe down the top of the screen to open up the notification panel and then tap at the top right to go to the settings menu.
2. Scroll down to the Personal section and then tap Lock screen and security.
3. Tap Security lock settings.
4. Slide the ON/OFF switch next to Lock instantly with power key to the right to enable and set the Power key as the screen lock key. When the switch turns green means this option is enabled and you can instantly lock the screen whenever you want simply by pressing the Power key.