Laying Jump Up Thing - How to please?

Ok well I'm a black belt in tae kwon do so this shouldn't be an extreme problem for me but I've been trying to do the jumps where your laying down and you jump up on your feet. I wasn't taught how to at my school so I was wondering if any experts know how to and could explain it to me, cause I think I may have been doing it incorrectly considering I have a headache and back pain now lol. Please and thank you!