Hi,
First, you go here: http://www.shipsim.com/downloads/patches.php
And you update your game to 1.1 and download and install the mission editor.
Then you take a look at the Mission Editor manual which you can find in your shipsim 2008 directory, to get you started.
Alternatively, you can also use this manual by mvsmith:
http://www.shipsim.com/ShipSimForum/index.php/topic,3653.msg37878.html#new
That should be enough to get you going, I hope.
Fred
