General information about the Custom Scenery Folder:
In the X-Plane 10/11 main directory there is a folder called "Custom Scenery". In this folder resides the additionally sceneries.
Some scenery are already included there (our Aerosoft airports, etc. ..).
Next there is a file called scenery_packs.ini (or only scenery_packs).
In this file, all in the Custon Scenery folder located scenery are registered.
An example entry looks as follows:
...
SCENERY_PACK Custo