How To Screenshot On Moto G-Please Assist me?

Hello guys

I recently bought a Moto G smartphone from smartprix.  I would like to capture the screen of game I am playing on this phone and send to my sister who really badly wants to see the real layout of the game on the screen before she can download it.  However, I am unable to utilize most of its features, since I am still a newbie to this Moto G handset. I have had several rumours about this phone being capable of taking screenshots without installing any app. How do I do this?  Every information is highly appreciated…TIA