Hi Dori, Thanks for contacting us! You can add additional images by dragging them on from the Photo Basket at the bottom of the editor. You can also then right-mouse-click on the image you’ve dragged on to send it to the back.
Normally you would start by uploading the image you want to use as your background, and then drag on any additional images from the Photo Basket, but this will only make a difference if you want to erase areas from the foreground images.
Let us know if you have any further questions!