I'm going to be ridiiculous, and put in a serious answer.
When you hit the ground you want to do a 'high fall', landing on your side, hitting with as much of your body as possible, from your leg all the way to your arm. You even want to hit the ground a little with your arm when you come down. If you land backseat like that, your bindings will pop off, and take some of the impact too.
There's really no point explaining it, you need to go find some mats, and a Judo/ Aikido teacher to show you what to do.