creep spawn
Creep spawn is simpler that you think. Create regions where you want the creep to spawn. Then make the trigger something like this:
Event: Periodic Event (However often you want them to respawn)
Condition: (Region Name) does not contains any units (0, 1, 2, 3 units etc.)=True (Not required, but you dont have a control system like this, then creeps continue to spawn and you'll find theres about 20 of them spawned when you go to hunt them.)
Actions: Units-Create (number of units) for (player x) in the center of the region. (If you had a big region and wanted them to spawn at random places, then use random places in the region.)
That should do it. Good Luck
-Blue