Adding User to Local SBS Server Admin Group

I am not entirely familiar with the closed off nature of Windows SBS when it comes to Policies, etc.

I need to found out how to add a specific User (Std AD User) to the ‘Local SBS Server Admin Group’ so that I can install software as that User on the server.

I also need to set the Policy to allow this user to Logon Interactively, which I seemed to have set under the Local Policy User Rights Assignment but this did not work. The user is only a Member of the Domain Users.