Read a few tutorials? Not sure how everything fits together? Here is a complete mission showing everything you need to know. Includes goodies like gear selection.
Play it (its a fun little mission) then take it to pieces in the mission editor. Use the files as template for your own mission.
The OFPEC Command Reference contains details of all scripting commands available to the editor.
All you need to know about how to start editing.
This tutorial explains the mysteries of multiplayer editing.
OFPEC hosts several quality tutorials written specifically for the site by staff and members...
Register a tag, browse for addon keys...