After you install Service Management Automation (SMA) there are two groups created on the SMA server. There are the MgmtSvc Operators and smaAdminGroup groups. The MgmtSvc Operator group provide access the Windows Azure Pack Admin Site. The smaAdminGroup provides administrative access to Service Management Automation. As a best practice, I suggest creating Active Directory groups and add them to the local groups. Then you can manage your permissions in AD.
If you see the message: “User does not have permissions to access the Service Management API.” Just add the user to the MgmtSvc Operators group.