First of all, you have to have an Ambipom that is female ( a red ♀ symbol), then have a Ponyta that is male (a blue ♂ symbol). Teach the Ponyta Bounce and then put it in the daycare with the Ambipom. When an egg is made, it should hatch an Aipom with bounce, evolve the Aipom and BOOM! Ambipom with Bounce.
Hope I helped! :D