After each image there is a "buy" button. From there pick a print type and then pick a size. If you are unfamiliar with the descriptions like "wrapped canvas" and "metal prints" there are videos there at the order form and I have included links to them below.
I know they are popular, but I really don't like or recommend 8x10 from a SLR camera. The reason why is that it is a shorter rectangle. To make the short side fit on the paper you have to lose 20% off the length of the picture. I still make them available because they are popular, but keep in mind that if you order them you will have to pick what you will lose of the long side of the picture. 16X20 has the same problem and to a lesser degree so do 11x14 prints.
The only way to keep the full image end-to-end is to pick a full frame size. 4x6, 7x10, 8x12, 10x15, 11x16, 12x18, 16x24, 20x30, and 24x36 are all (roughly) full-frame sizes and you should see the whole image. For canvas, thin wrap and metal prints I only sell full-frame sizes since they are ready-to-hang.
Canvas Prints Explained - http://www.smugmug.com/prints/giclee-canvas-watercolor
Thin Wrap Prints Explained - http://www.smugmug.com/prints/thinwraps
Metal Prints (not the same as metallic surface prints) Explained - http://www.smugmug.com/prints/metalprints