If I wasn’t clear in my previous post, you have to run “openvas-setup” as the first big step to installing openvas which includes installing the openvas-management. Then, you should repeatedly run the script “openvas-check-setup.sh” until every issue is identified and resolved.
If you’re asking about the Adminstrator User Account, create the User as I described, whether you specify the Administrator role or not, it will be given Adminstrator privileges.