How do I create a postmaster account so I can verify my account to a email processor like SparkPost?

How do I create a postmaster account so I can verify my account to a email processor like SparkPost?

Okay, I have a domain, I have a admin account and I can't seem to create an account so I can get an email from SparkPost. This is insane that there is no way to do this.

Any help you can provide would be greatly appreciated.

Drew Nathanson