ok before you can put an image in ape you need to do any image changing(editing) you want to do in a graphics program like Paint or Photoshop etc. That is also where you will do any resizing as well. Remember when resizing a smaller image bigger if you go to big the image will distort and pixelate meaning you will see individual pixels in the image instead of a smoth looking animal coat you will have a more blothchy coat because the little pixels of color that make the image will stand out more.
to see what I mean by pixelate open your game and use the zoom in tool on the game map to zoom in as far as you can and see how the little pixels stand out. well that's what happens when you try to resize a smaller image to a larger image if you make it too big.