To be safe, learning to jump should be done with your trainer or find somewhere to take lessons if you don’t have one. I’m sure you can learn from a video, but you need knowledgeable eyes on the ground helping you.
Hi! There is a great article about this on the website of PraticalHorsemanMag! I share you the link: https://practicalhorsemanmag.com/training/points-to-consider-jump-with-the-motion-of-your-horse-11824
But also in my opinion the best way for you to be sure of your position is to ask your trainer or maybe you can ask someone to film you!
You should go into two point. You lift your self out of the saddle while your body is slightly forward, heels down, and elbows bent. You need a lot of core muscles and thigh muscles to do this at first(for me). I would recommend you practice this while the horse is not moving, walking, trotting, and cantering. There are lots of informational videos and posts about this on the internet so you could go check some of those out.