Check out the "onMapSingleClick" command in the Command Reference (and try a search for it as well, might turn up something useful).
You could use it to either directly to drop a single object to a point on the map or, for more control, pass the position array to a script and create and even choose the object from there.
Check out artillery scripts too - they often use onMapSingleClick and could be trimmed down to do what you need.