It's sorta like a mac program, lots of individual windows, and they aren't all enclosed in one big window like most Windows programs do. Could be a little confusing, but you should be able to figure it out. If it won't install, check their FAQ section.
I've played with it some. I had a problem getting the pics to a window where I could do anything with them but eventually got it. I can't remember exactly what I done so just keep playing with it.
Should be able to go to File --> Open and then select the picture to edit. When the picture appears, it should be in a window that is completely editable. On the other hand, you could also go to File --> New and set the dimensions for the new photo and a new blank window will appear that you can draw in.