Taking a screenshot on the Google Play Galaxy S4 edition is quite easy.  All you have to do is hold both power button and volume down buttons at the same time.  Hold those 2 buttons until you hear a sound and see screenshot you just took.  For some reason, if you let go of the buttons too soon, it will not take the screenshot.  Below is a video of me taking the screenshot, and also a screenshot I took of my Galaxy S4.   take a screenshot Galaxy S google play edition