Turning off My Photo Stream can help you free up some space in your iPhone/iPad through deleting all Photo Stream pictures from your device. Hence, this text describes how to turn it off for your better understanding.
Steps to turn off My Photo Stream in iPhone/iPad:
Step 1: Access Settings.
Step 2: Open Photos & Camera.
Step 3: Click the switch beside My Photo Stream to turn it off, and choose Delete in the pop-up menu.
For more direct illustration, pleas look at the screen shot below.
