Importing A Png Sequence

Does anybody know the correct way of importing an animated background? In the Game Mind Map I create a New UI, double click on it and drag the PNG images over Image. When I click play though it just shakes and it's not animated. I've just started with Buildbox.

 

I think it's called "Parallax Effect" http://help.buildbox.com/buildbox-features/parallax-effect

 

Try adjusting the background speed.