remboi

Alrite everyone! i jst recently got paint.net and started using it, but i came across a poblem that i dont know how to overcome. I have created two images sepratly, but i want to cut a piece out ov one, and put it ontop of the other one, so it comes through. Like if u cut a hole in a piece of card and put an image behind it so it shows through. However when i try this i get the background cutting out the image. Any help would be greatly apreciated. Thanks remboi