This is very timely as I downloaded that art bundle yesterday to make an icon for a new Mac app. Can someone tell me how to use that Apple Photoshop template f

This is very timely as I downloaded that art bundle yesterday to make an icon for a new Mac app. Can someone tell me how to use that Apple Photoshop template for app icons? I've been using Photoshop since version 1.0, I understand layers etc, & I'm still baffled. I get that when you save it generates all the sizes and puts them in a folder. That part works fine. I don't get how you are supposed to propagate your artwork from the 1024x1024 section to the other areas of the template. I don't think you have to do it manually. I also don't see the ideal way to place your art inside the template roundrect - I'm currently selecting it with the magic wand and doing "paste into" which works, but doesn't seem ideal.