In this topic on the Missions board:
http://80.95.161.114/shipsim/forum/index.php/topic,2886.0.html (http://forum.shipsim.com/index.php/topic,2886.0.html)
You can find a tutorial on the Mission Editor and manuals on playing missions and operating various ships.
You must register your SS08 license key in your forum profile to access these documents.