Controlling an object placed by a class

maybe this has been asked millions of time but can’t find any answer.
i have a MC with a class attached, this class place another MC with an animation.
i have another mc with a class wich place a button.
how can i tell the button to tell the animation in the other movieclip to play?
i dropped both mc to the stage so they are at stage level.
getting mad. thanks in advance