What
do, you have?
If you have any existing art, you can scan it (but designs are rarely 8 x 10) or take a digital picture with the camera very parallel to the art so it doesn't distort.
Now trace or digitize the outline with the pen tool in Corel or a tracing program like CorelTRACE or Adobe Streamline.
Scott Fresener has an article about improving art you plan to trace:
U.S. Screen Print & Inkjet Technology