Be wary of spinning before you get a clean pop off the jump. Usually when people start out they're overly anxious to spin and get it around so they start spinning before they've popped off the jump properly which means either catching an edge or landing backseat. Get a good solid pop with some forward pressure on your shins and then initiate the spin.
I recommend starting to on a tramp, it helps you get the feel of it. Try starting on smaller kickers first. Take your time and don't feel rushed because at the end of the day it's about having fun. After coming of the lip try like putting your arms in a t position like the other guy said and use the momentum of coming of the lip to bring your self around. Keep researching and learning about 360s as much as you can. You got this, believe in yourself and most importantly have fun!