You need a Trigger (Actor > Triggers > Trigger), a CreatureFactory (Actor > Keypoint > ThingFactory > CreatureFactory) and a Spawnpoint (Actor > NavigationPoint > Spawnpoint). Put them in your map and change the following settings:
- Trigger:
Events > Event = A
- CreatureFactory:
Events > Tag = A [same as Trigger's Event]
ThingFactory > capacity = [total number of monsters]
ThingFactory > MaxItems = [total number of monsters that spawn together]
ThingFactory > prototype = [type of monster from Actor > Pawn > ScriptedPawn > you choose]