Licenses need to be transferred by the original PSIO Cartridge owner. The owner needs to login to their account here and then proceed to the ‘Account Details’ options in order to change their email address. Once they change it to yours, you can send a request to reset your password by attempting to login to the account. Once done, you will then be able to login using your email address and use it for firmware downloads.
If you have purchased from a wholesaler (EG: Stone Age Gamer), there is no way to change the email address. It is locked to the wholesaler.