I think I can help you! I checked out your book and noticed that when you clicked on the sticker, although it was a circle, there was a white square as the background. You might want to download an editing app like PicsArt (free) and load the cover, then press 'add photo' and choose the sticker. Then you can choose blend and set it to screen (I think that's the right one.) since doing this will get rid of the white background and leave the round sticker. Hope this helped! If you're having any trouble, you can PM me and I'll be happy to help you do it! :-)