How do I create in Animate a close button for a banner Ads.

Check out this general post to remove a div:

https://stackoverflow.com/questions/19704477/adding-close-button-in-div-to-close-the-box

or specific to google:

https://support.google.com/webdesigner/answer/7611803?hl=en

I suppose you are doing HTML5. You can add a button element (as opposed to the movie clip ) by pressing F8.

They have 4 frames 

The code will be something like this (add a url on click for example).

this.closeBtn.addEventListener("click", fl_MouseClickHandler.bind(this));

function fl_MouseClickHandler()
{
	window.open("http://www.adobe.com", "_blank");
}

To close the add, you would need to hide it.