If you haven't received your registration within that period of time please send email to email@example.com. It might be that email adddress you specified in paypal just isn't working.
Also, please add firstname.lastname@example.org to the safe senders list, if you're using anti-spam program/blocking/safe-senders settings. Otherwise, you won't receive the registration file, and it will not be possible to contact you about this matter. Thank you.
Save received registration file somewhere on the hard drive and then open it by clicking on Register as shown below.