if the picture is complete, draw (you might want to do this on a copy) a grid on top of your picture. Use one inch squares...so it is best to do your design in even inches. then get gridded pattern paper, draw your squares on the paper as big as you need... a 2 x 2 grid would double the size of your pattern... a 4 x 4 would quadruple it... once you have your dark grid lines drawn on top of their light lines, you will take each single square on your little pattern and reproduce on the big grid.... it is not difficult to do...