Sorry for the delayed reply. White is not transparent. In nearly any program, when you're using a transparent background it will be displayed as a checkerboard pattern. It sounds like you drew directly onto a white layer and not a transparent layer. Also be sure to trim your images before saving them. You should NEVER have an image floating in the middle of a giant field of empty space, this is incredibly un-optimized for your game and for Spriter. I highly recommend you learn to use Krita from www.krita.org its a fantastic and FREE graphics program with much more professional features and much better geared for game art creation (or art creation in general)
If you want to keep using MS Pain, then you'll have to Google "save image with transparent background in MS Paint" or something like that to learn how to do so (if it's possible. I assume so, but don't use MS Paint)
