Buffalogirl, all you need is a Tshirt, and an iron on transfer sheet for your printer. You can buy them at Wal-mart, even! They are located in the office supply section... I think mine is the brand Avery.
You simply print the image, but be sure that you tell it to do the mirror image (if there is any printing). It is a printing option.
The transfer sheets will come with their directions.
You should search within Creative DISigns. You may find a lot more images by other talented members as well!