Take a Screenshot on your iPhone or iPad in iOS 11
Screenshots are incredibly useful. In fact, that's how I made all of these guides. Taking a screenshot is very simple:
Press the Power and Home buttons at the same time and release,
like pressing the shutter on a camera. You will hear the "Camera Shutter Click" noise as long as the Silent Switch isn't on. You will see a mini version of the screenshot pop up in the bottom left of the screen. If you're having trouble making it work, start by pressing and holding the Power Button, then press the Home Button, then release both – it becomes easier with practice.
You can ignore the mini screenshot and it will go away after a few seconds (automatically saving it in your Photos), or you can swipe it away (still saves to Photos), or you can click on it if you want to immediately Mark it up or Delete it.
You can always Mark it Up later - go to it in Photos, click on it, click Edit, click the THREE DOTS for More - Click Markup (or More again to choose another photo-editing app) and then play with the markup options.
Find out more about the markup tools in my guide "Scan, Sign, and Send a PDF," or for an in-depth look at all the awesome things you can do with screenshots and Markup, check out this Gadget Hacks article: https://ios.gadgethacks.com/how-to/18-tips-for-ios-11s-new-screenshot-tool-your-iphone-0178452/