Hello. You will want to cut the kids out from the background, unfortunately those shadows could prove to make that difficult. Pictures with a well defined and very plain background would make the processes easier.   Either way, with whatever images you choose, there are lots of ways to separate objects out from their backgrounds. And I will show you how.... First, you will need to know Paint.net's User Interface http://www.getpaint.net/doc/latest/MainWindow.html, Layers http://www.getpaint.net