When we use ssl certificate in tableau then first buy the wildcard certificate and then use it. Certificate cost based one.
When you try using creating crt then that is not in use. You can send to that crt to certificate provider and pay the money.
read: Send the CSR to a certificate authority to obtain an SSL certificate in url above.
Whatever you created then we can get ca to obtain ssl. But that will be cost based and not free.
When we buy ssl then go with wildcard ssl certificate.single wildcard, will use in you company n number of domains.