Hello!
It looks like the only payment method currently available is donation via Boosty , semblance of Patreon, which belongs to the DonationAlerts company
It's quite simple, and the main thing is that you can use PayPal to pay and you don't need to register

how to pay guide
37 sec tutorial in youtube
one more tutorial
here is a tutorial too
Feedback about using https://www.furaffinity.net/journal/10161490/

A few remarks:
now the service may be under load due to the large number of new users
so if something goes wrong, don't panic, don't press the same button many times
perhaps payments >$400 should be divided into two smaller payments

Thanks!