Once you start the game as single or multiplayer and END#1 (or 2, 3 etc) trigger will cause the game to end. In a single player mission this will then show the "End-Loose" outro if you have made one, then goto the debrief. If its in multiplayer then you will go straight to debrief (intro and outros dont work with Mplayer). Depending on the END# trigger, or the Loose trigger you can set up different debriefs that show.
So for example your END#1 trigger could be for the debrief;
"Congrats you saved all the civilians"
END#2 could be;
"Congrats, but some of the civilians died"
End#3 could be;
"You are alive, but there were huge civilian casualties".
And then your Loose trigger could be;
"You are dead. Your mission is a failure".