Are you working with a trainer? Do you know how to jump well yourself? (Stay out of their way, not left behind or ahead of the motion, no catching in the mouth, keep your balance), how much experience do you have riding? How much training do your ponies have? Have they jumped before at all?
Wait, you've already started jumping them, but are asking how to introduce them to jumping?
Jumping can be very dangerous if you are unclear on what to do. Please, PLEASE consult a trainer. You don't want to end up injuring any of your horses or yourself because you think you're just having a bit of fun with them.