SMAUG comes with a startup script. You have to log in to the server via telnet and run the script.
If you are running on Unix/Linux, see this for an example:
http://www.gammon.com.au/forum/bbshowpost.php?bbsubject_id=3469
If you are running SMAUG on a Windows server it should set itself up automatically as a service when you run it, and restart itself when necessary. You just have to run the service (this may need to be added to the list of startup programs.) However, it's much harder to run the program on a remote Windows server, especially if the remote server truly is somewhere far away (as opposed to in the room next door.)