How to add user to Administrators Group I am using OS X Mavericks Server. I want to add a user to the Administrators group but none of the built-in groups show up under Accounts -> Groups on OS X Server. 

How can I manage users in the Administrators group?
The most common use of admin with Server.app is to run server.app and administer the server itself.

If that's what you want, use Server.app to tick the administer this server box: