...Use the "Register Serial" option to put it into the registry, then proceed with Activation as above.... This is not an option in the email I got with my order number
Please, check that email better: I'm sure there IS a Serial Number inside, assuming this is the email you received when purchasing.
If you are not sure this is the actual email receipt and you think you lost the original one, as explained on the manual (fsdt_install_guide.pdf, page 9) and on the thread
here, you can retrieve another copy from the Esellerate support site, address is given both in the manual and the above thread.