u save u'r mission as user mission ,press ALT + TAb , or quit the game . then go to this :
C:\Users\[YOU'R USER NAME ]\Documents\ArmA 3 Other Profiles\[YOU'R INGAME USER NAME ]\UserSaved\missions\.
And pbo you'r mission using CPBO or any tool u like . im not sure if this info is accurate . cuz i dont have arma 3 yet
im too lazy to write it again.
Added 1 minute later:
1. Get any tool capable of creating .pbo files.
2. Got to your ArmA3 folder under documents, look for the folder containing your mission.sqm
3. Create a pbo of that folder.
4. Use that pbo as mission-file.
The export function in the editor seems to only package the default files, so you're better off using an external program for that.
this was copyed from another post i made . the save function doesn't save anything excluding mission.sqm . you have to manually add them to you'r mission , and pbo it ,and move it to MP missions folder.