You can create a sprite, make it small 3x3 or so. Set the properties initially visible to unchecked (so it isnt visible). For the sake of this we will call them spawnLocation.
Now just copy paste these to each spot you want to be an option for randomly summoning.
System > Pick Random Instance will allow you to choose spawnLocation object.
Then Create Object (Whatever you want spawned) at spawnLocation.x spawnLocation.y
If you want multiple spawned and don't want them overlapped - add a boolean type instance variable to your spawnLocations set to false. Simply check for spawnLocations that are showing false when you pick your random spawnLocation.
tysm! i'll try that