This is a commercial application which means you can obtain it either in CD-ROM format or as a downloadable application. If you have the CD-ROM version, install it and use the CD-key that is printed on the CD sleeve. If you've lost the registration key, then a new purchase needs to be made to obtain a new one. The Amazon website lists the application as being available. Unfortunately, this is the only way to register the application.
The actual registration process can be done after the product is started and launched for the first time.