Enrollment is the process of requesting a certificate from Adobe. You can generate your keys and create a request that is sent to Adobe. Adobe then generates the certificate and sends it back to you. Adobe will not know the contents of the private key. Therefore, you must have a way to back up the key so that you can recover it in case of hardware failure.
Unlike the License Server, Packager or Transport certificate, the Domain CA certificate is not issued by Adobe. You can obtain this certificate from a Certificate Authority, or you can generate a self-signed certificate.
For instructions on how to obtain the Adobe Access credentials, see the Adobe Access Certificate Enrollment Guide.