To create a screenshot of whatever is displayed on the iPad screen: 

- Hold the iPad in Landscape mode. 

- Press and hold the Sleep/Wake/Power button (at the side-left of the device) 

- Immediately press and release the Home button (middle-right just outside the screen). See the two red circles marked in the image below. 

This creates a screenshot of the current display, and gets stored in the iPad Photos gallery (Photos > Albums > Camera Roll)

How to take a screenshot