Depending on how Server Enterprise Edition has been installed, either you can use the mfds command to start it, or it can start automatically when the machine is started.
To stop the Directory Server, you use a menu option of the Web interface.
To access the Directory Server using the Web interface, you start a Web browser and enter the address where the Directory Server is running.
Depending on how the Directory Server has been configured, and what you want to do, you might need to log on to Server Enterprise Edition Administration. To do this, you need a user ID and password.