Hi Kivamalik, Thanks for contacting us! There are two ways to achieve this:
1. If you would like the background to be filled with a solid color, simply use the Effects tab > Doodle tool to paint over the area you would like removed.
2. If you would like the background to be another image, first open up the background image, and then upload and drag on your foreground image from the Photo Basket at the bottom of the editor. Re-size and re-position the image, and then use the Eraser tool to erase the background. We have a brief demo video which demonstrates how this is done.