Landscape Layers

Hi all,

I have a landscape splitted in several parts. Each one of them are in a different level and these levels are loaded in a “master” level. What I would like to do is to sculpt on the landscape using non destructive layers. I did not activate “Enable layers” when I created the landscape. How can I avtivate that option now? If I select a piece of landscape the activate layers option is not there.
Any idea?