1) Creature Generator
    2) Trigger
CREATURE GENERATOR
    Place a creature generator and a trigger in a map. Right click on
    the creature generator and chose properties. We are concerned with "Events"
    and "CreatureGenerator" selection options.
Expand "Events" and there are two options: event and tag. Leave 
    event defaulted and chose
    anyname (such as tag1)for the tag.
visible--->pawn--->scripted pawn, then highlight the monster for the map. Close the Actor Class Browser then click the "use" button option and the selected monster will appear in the SpawnClass selection box.
Futher down there is GenRadius which seems to be how far away from the CreatureGenerator 
    the monster MIGHT spawn. The default is 32. If the CreatureGenerator is to 
    close to a wall the monster MAY spawn in a wall. Then there is MaxAlive and 
    MaxGenerated. They seem connected, set both to the same number. If the number 
    selected is more than one use TimerInteval to set how
    long between spawns. 
    TRIGGER
Highlight the trigger, right click and select properties. Expand "Events" name the Event the same as was used to name the CreatureGeneartor-->Events-->Tag in this case (tag1) and type in the name trigger for the Tag.
Expand the "collison" option The "collison radius" seems 
    to be how far away from the placed trigger the player can be when the monster 
    spawns. This can be seen vissually in the map but only in a 3D view window.