Step 1: From any screen, press & hold the Sleep/Wake button, until the iPhone’s Shutdown screen comes up. (talking about the Power button available at the top of your device, if you’re owning an iPhone 5S or earlier version. The iPhone 6 and later versions have this button re-positioned on the right side).

Step 2:
 Now, press & hold the Home Button until the iOS home screen is displayed. This signals that the Random Access Memory flush has been completed!