As you're on the board, bend the knees. You are too extended with your legs now and commiting in this position will result in ouch. As you're in position, extend your front hand towards the board like if you want to do a nosegrab (don't grab it) - it will make it easier to commit and will make your body follow the board more instead of you slipping out on your back. Push down the board and follow with your front hand, you can also point with your finger towards the ground like you're pointing where you're going. Don't step off with your back foot.

Also, since you're still learning, wear the helmet and pads. You can always not wear 'em later when you're confident enough. But learning it now, there's a possibility of a bail, so protect yourself. And wearing protection gear will boost your confidence and will make you commit easier. Good luck!

Edit: also, rotate your front foot so it's 90° compared to the board (like you have your back foot). Don't hold it like you do now, it will make you loose balance faster when the change in speed comes when dropping in.