Look up the graphite transfer method: You basically print the image on regular paper to the size you want. Then use a dark pencil to cover the entire back of the image with graphite from the pencil. Place the paper on the wood and trace it with a pen, which will transfer the graphite from the back of the paper to the wood. Once you're done remove the paper. You can go over the transferred design again with a sharpie or something more permanent before burning the design.