1.) Click and briefly hold on the "Order Print" link below the thumbnail, then choose the size you want. (This didn't work before, but it does now.)
2.) OR: Click the thumbnail to see the image larger, choose a size from the pull-down menu and click "Add to Cart."
Once you have made your choices, click "Shopping Cart" in the lower left or the shopping cart icon. You'll be taken to a page with your selections where you will have the option to change quantity or adjust the crop of your pictures.