Heather, what you're taking with the mobile app are panoramas - not photosynths. A flattened out version of each panorama is saved in your camera roll as a JPG image if you wish to print them, however, due to RAM constraints on the phone the panoramas are not very high resolution.
If you want high resolution panoramas to print, you'll need high resolution photos to begin with. From there, you can use one of many free panorama stitching apps to stitch a pano. I reccomend ICE for Windows for ease of use. http://bit.ly/microsoftice From ICE you can either upload to the Photosynth site to share online or export to your hard disk for printing.
@veryoldtimephoto, you should look up Henri Astre's PhotosynthToolkit. Running steps 1 and 5 will get you the original resolution photos along with the original metadata, which is useful when you want to give credit to the original photographer. Remember that you should only download photos whose licenses give you permission.