i'll try to help with the mission editor a bit for the newer guys, since im new too:
A really quick way to set up skirmishes in the editor (for real beginners):
Open the editor
press F1 to be able to place units including the ones u can control.
in the map u double click on the surface to place the units. u need to select their side, category and type. this can be figured out easily. u can also select their skill.
make sure one of the units is "PLAYER" to control it. u can also choose a few "PLAYABLE" units to be able to switch between them while playing.
notice that u can select units and press ctrl+c to copy them and ctrl+v to paste.
holding shift will allow to rotate units and waypoints and such.
when placing a few units u can link them to groups with F2. just drag a line from the soldiers into the leader of the group. the cyan line represent who they follow. link a few troops to the same soldier to have him be the squad leader.
now way points. u must give every unit (or the squad leader, which represents the entire unit) at least 1 way point or the AI will be brain dead and wouldnt know how to act. AP doesnt just tell the AI where to go but how to behave.
select squad leaders and give them way points (pressing F4 and double clicking on the surface) telling them where to go. a move command is easy and u can place the last way point near one of the former way points and choose that last way point as CYCLE and the units will go from that cycle way point to the nearest WP and patrol on the same way points again and again until engaged.
i recommand a GUARD way points (last in list). its most simple use is to set units to be at that location but if any other unit on the field (on the same side) encounters a rival unit than all guarding units will know of their whereabouts and engage them.
with GUARD all u need to do is just place a GUARD WP and that's it. just one is enough.
next is triggers that can set when the mission ends (among many other things). the most simple winning condition is when all enemies within an area are dead.
u place a trigger (F3) and set its size from 50X50 to something else. bigger.
then u set it from "none" to , for example "OPFOR" and below to "not present"
and in the type of the trigger beloew u set "END1".
this means that if the opfor are not present withing the trigger area than the mission ends.
really simple and can be done in 5 minutes or less.
about the random missions -
u can choose F1, than instead of OPFOR or BLUFOR u choose - "game logic" and instead of "locations" u set "modules" and on the right u choose "secondary ops" or something like that.
u place this "unit" on the ground and it will look like a blue square. press F5 so SYNC that blue square to the unit which is the PLAYER. that's it. now when u r playing that module will give u secondary ops.
for far more details about triggers, units and waypoints check this: