Using your Samsung galaxy for a while, you might need to perform a hard reset on your device maybe to free up some space, cleanup virus or reset password. With this few steps you will effectively reset your Samsung galaxy S6

Step 1
Power off the Samsung galaxy S6 you are about to reset using the power button

Step 2
Press and hold the volume up button, the home button and the power button all at the same time until the Samsung logo appears on the screen.

cont. http://www.androidcare.net/2015/05/how-to-hard-reset-samsung-galaxy-s6.html