Combining Multiple Images Into One In The Library

[Gamegirl31 3]

I'm having a problem combining multiple png images in the library so it looks like they're all one image, for example, I have a png of Female Jesse from Minecraft Story Mode, and when I try to add a cube for the top of her head, the barrette and the back of her head, they show up separately instead of on Jesse in the library. Even when I add an image of the outfits from Ivor's collection that she wears in the game. Is this a bug or is there something wrong with my computer?