Embarrassingly basic question here. Using Photoshop, I've made a series of 4 sprites I'd like to use as sub-images for a single sprite. But for the life of me, I can't figure out how to import these using the sprite editor. I've added them as sprites to my resource tree, but when I create a new sprite, then click + to add a frame, it will only let me draw on the new frame -- I can't figure out how simply to make a second frame out of a pre-made image.