I learnt by just getting out there and trying it. Tip: Stay in the kids slope, don’t try anything fancy, and be prepared to look a fool :) Also get some ass-cushion pants and take the wristguards, that will save your lower back and wrists alot of greif.
Deep, soft snow is the easiest to start with, so try off-pist, or atleast try to stay off the rough patches. If it’s an icy day do something else, icy slopes makes snowboarding atleast 5x harder, as well as the falls.
Best of luck.