When you create the deck, a "window" should pop up so you can create all the cards. At that point, you can either drag images from your computer to that pop-up "window" or from your Art Library. If you use your Art Library, it must be from the side panel (on the right-hand side of the screen). Just search your library to find the images you want. If you drag images from your computer, and those same images are already in your art library, be aware that that image will now be in your library twice and will take up twice the space.
