Set the height or the length to the closest values of the desired print size. I selected 5 inches for this demo, which will result, due to aspect ratio differences, in an image that's slightly longer than 7 inches. I also selected "Bicubic Sharper" from the drop down box associated with the "Resample" area. I use Bicubic Sharper for down-sizing, and Bicubic Smoother for upsizing.