You use triggers of the type, end#1, end#2, lose ect. Using multiple triggers you can create "and" and "or" statements.
I'll give you some examples to make it clearer.
Eg.
Trigger - End#1 - east - not present
Trigger - End#1 - west - present
Trigger - End#2 - west - not present
This would make the game end:
If the east are dead, and the west it alive
or if the west is dead.
That's how to create objectives, if you mean on the breifing then that's completely different. If you do mean the breifing, then it would help if you posted the breifing you're using.