It's really simple and really silly too. You squirt some whipped cream on a lever, spin the spinner and then twist the handle up to the number you spun. So, you could spin a three but only twist the handle once if you wanted. Your points are double your twist amount : twist 2, get 4 points; twist 3, get 6 points etc.
There really isn't much else to it so I'll leave you with these video's: