Make sure AtB is on. Go to the Briefing Room and add a New Contract, under Add Mission. Also works during a normal AtB contract. Select your Employer, Enemy, World, Pilot Skills, Unit Ratings, Mission Type, etc. Once everything is set to your liking, go to the world during the contract time frame, and hit [GM] Generate Scenarios (with GM Mode on of course). May have to hit it a few times as I think it is just doing the weekly battle roll for each button push, as in you may get a no battles result again.