Follow my guide:
1. Go into your mission and put down unit/s that you want, if its just you and your friend then put down 2 soldiers.
make 1 solder the player, and make the other playable.
The more people you want to play in your mission then add more units and make them playable.
2. As for coop your going to want to setup a respawn, the most basic respawn is a base respawn, i have a tutorial here:
A quick rundown of that tutorial:
1. start a new notepad document
2. name it Description.EXT
3. put the following in it:
respawn = base;
respawndelay = 5;
4. In your mission in the editor put down a marker
, the marker's name will be based on the faction your units are on, so if your units are on the Blufor side then for the marker's name (not the text) put respawn_west
if your units are Opfor then name the marker repspawn_east
(refer to my tutorial for further info.)
Note the marker you put down will be where you spawn at when you die.
respawn = base means you will respawn at the marker (base)
respawn delay is the time before you respawn, so respawndelay = 5; means in 5 sec you will respawn again.
5. Put the description.ext in your missions folder, thats it.
Host the mission or put it on a server and then you should see units to pick from.