This is how i did it:
Edit with notepad the Combatfs.cfg file in your main combat flight simulator folder.
Add the following 2 lines to it
[LAYOUT_TOOL] 
Scenery_Edit_Enable=1

Note1: If you are a newbie and don't how to insert a new section/key inside the config file without breaking up the existing ones, just insert  those  2 lines at the top of the  Combatfs.cfg file. It will work fine.

Note2 : If you are not a newbie (like myself) to CFS scenery creation, then this is probably all you need to know.

Goto the Freeflight option of CFS  and select the location where you want to add some scenery.
Select the Scenery Editor Option on the World Menu.