Some of my photos have already been uploaded to photoaccess. In this case, all you need to do is follow their directions to order prints.
Otherwise, you will need to upload the photo you want. For example, let's say you want to print out some of the photos from my web site. Find a photo that you want to print out. Make sure you are viewing the full sized photo (not just the thumbnail -- click on the thumbnail to view the full image). Click on the full image with the right mouse button (press and hold the mouse button on a Macintosh). Select "Save Image As..." (Netscape) or "Save Picture As..." (Internet Explorer) from the menu and save the photo to your hard disk. Now upload that photo (and any others you want) to one of these services (following their directions) and they will take care of the rest.
Again, remember that higher resolution photos will look better when printed out (higher resolution photos appear larger in your browser window). If there is a thumbnail, be sure to save the full size image, not the thumbnail.