Hi,
I try to understand, but from the picture you’re showing, it seam you’re landscape doesn’t have any material, or you’re material doesn’t have any layer ?
Hard to tell without more information…
But in case, try to assign you’re landscape material instance to you’re landscape. By clicking on you’re landscape in the world outliner. And drag and drop you’re instance in the details panel of the landscape, in material.
If so, the layer normaly show under the ‘‘target layer section’’.
Hope it’s help, Have a nice day !
that is what I had tried before, I’m not sure if it has to do with the landscape or the material itself. I was messing with it for about 3 hours last night and couldn’t figure it out.
Hi,
Without knowing more about you’re material or landscape, it’s hard to tell something…
To try :
First,
If you try to put the material instance while being into the landscape editor. This is wrong.
You have to do it by the world outliner in object selection, not landscape editor.
When you’re instance is assigned to you’re landscape in the detail panel under material, you can go into landscape editor and then the layer normaly show.
Second,
You can eventually try into a fresh level ?
Third,
Tutorial like this one can probably help you to find what’s going wrong ! 
Hope it help or you have already found the solution !
Have a nice day.