How do I get the default local Admin user back?

How do I get the default local Admin user back?

When I first setup ADSelfService Plus, I created super admin accounts and then deleted the default local admin account.

Now I am trying to add multiple domains in ADSelfService Plus but I believe I can only do that in the Default Local Admin Account.

When I try and add a local Admin back in, the domain field doesn't have a section for local authentication anymore. How do I get the default local admin account added back into the system so I can add more domains?

                  New to ADSelfService Plus?