Here's how to take a screenshot on iOS:
1. Go to the screen or app that you want an image of.
2. Make sure that the image is set up according to what you want the image to look like.
3. Click Home button and the On/Off button at the top right of the iPhone or iPad at the same time.
For iPhone X, click the button on the right side and the volume up button on the left side of the iPhone at the same time.
4. When you press both buttons correctly, the screen will flash white and there will be a sound like a camera shutter. This means you've successfully taken your iPad or iPhone screen capture.
5. To view your new screenshot, go into the built-in Photos app and then tap on Camera Roll. In the Camera Roll, the most recent photo will be the screenshot you just took.