The Windows key and G.
This will open up the Game Bar (Xbox) that is built into the computer.
The videos (or screenshots) are easiest found by the following.
Type in Xbox in the search bar > then selecting Game DVR on the side menu (4th option on the side menu below, you will see it with a light grey box around it.
Embedded below you will see an animated GIF as well as a 45 second YouTube tutorial.
Thanks for reading!