All you need is an SD card.
In the menu system, tab all the over to the right to the Accessories menu tab. Turn screen snapshot on. Now, every time you press the “mark” button, the unit will write the contents of the screen (whatever screen is displayed) to the SD card. You’ll also get a waypoint with a camera icon displayed on your chart screen.
Congrats, welcome to the club, and be sure to share your screenshots with the rest of the class!