[Map] Where does new map data go?

When I add extra maps in advance map how do i know where the actual map data itself goes? Let's say I repoint all of the map banks.. when i add a new map to that bank, it doesnt ask me for an offset. Where is the map data going? I want to know so I dont end up overwriting something. Does it automatically find free space? I mean the data for the map itself has to exist somewhere, or do I need to repoint something else? Sorry guys I'm just really confused with this one.

Using A-Map. When you create a new map. It will ask you the size of your map and the graphics you want to use.
At this time, your map is not inputted into your ROM yet, as it is only A-Map File. There should be MAP FILES directory at the very bottom of your map list in A-Map
There is where you can find your created map, just remember you have not put it inside your ROM yet.

To insert it to your map, head to INSERT MAP icon just next to the CREATE NEW MAP icon.
A-Map will ask you whether you want to replace existing map or create a new map. Insert the desired offsets.
Then your created map will be written in your ROM.