Im not the best at these but heres how it goes in general
To jump
Contract or relax kness and bring your legs under your self
Being on your toes instead of flat foot will help you jump higher
Landing
You need to make sure you dont off balance when you launch
So landing needs a good launch
And in mid air you can gain spin by tucking your limbs and neck
And you can open your body wide and long to slow down spin