Your very first time on a snowboard with both feet strapped in and actually moving. Figure out whether you are regular (left foot forward) or goofy (right foot forward), then stick with that lead foot for now so you build one consistent habit. Point the board straight downhill ride a little, and slide with your knees soft and weight centered. To stop, turn the board perpendicular to the slope and press into your heel edge. That's a heel-side skid stop. Next article will get you to practice toe-side stops too: same perpendicular finish, but press into your toe edge so you can stop confidently on both edges.
Here is a video explaining how to slide and stop:
Source: SnowboardProCamp · How to Stop on a Snowboard With Confidence
Key tips
- Keep your knees bent and back straight
- Look where you want to go, not down at the board
- Start on the flattest green slope available