I found the following code on another forum post:
Alarm=100 //it is about 4 seconds
instance_create(object0,random(room_height),0) // if you want that new object appears at random position
Alarm=100 //so it will create new object every 4 seconds
Edit: I have made the objects fall vertically, however even when I put the repeat action in, the event only happens once?
Also, the only way to make the objects spawn is to place one in the room, which just stays stationary. :/
Edited by GameVC, 28 November 2012 - 07:45 PM.