To take the screenshot on iPhone X, you need to follow few steps:
- First of all, you need to open the application or the screen that you need to capture
- When you open the application or the screen set up everything you need to shot
- When everything has set up you need to press down and hold up the right button of iPhone X and with that click the volume up button at the same time to capture the screen.
- The screen will just show flash and the screenshot is ready for iPhone X.
For more detailed information see this video to completely understand: How To Take Screenshot on iPhone X.