Welcome to the forums!
I remember I got this when I was quite young. I put it away for a few years, and pulled it out again and was able to figure it out. IT's a tad knacky, but nothing you won't pick up quickly. I would recommend that when you're learning and practicing, that you use a stronger gimmick - either look around your house for something stronger or triple/quadruple the gimmick. That way if you mess up, you don't have to reset. Do this just while you get the basic mechanics.
As far as the mechanics, it needs to be as steady as possible. Imagine the center of the card must remain in the same spot as much as possible. Then you pull your hand back (causing the card to spin), and make sure to NOT throw it. The motion eventually needs to be quick to make it spin lots, but when practicing it can be slower. There is a bit of a wrist flick (as if throwing a Frisbee that has to remain in the same spot) but it's more about pulling your hand back to counter the forward momentum of the wrist flick.
Imagine the card cannot leave it's location. So do not throw it like you were Ricky Jay.
It takes so much practice, but is super fun once it's achieved.