When asking for Terrain help, you should post an image of your existing terrains.
If I understood these tiles correctly, the labels should look something like this:
(Note, however, that this tileset is incomplete and Tiled will struggle to give you great shapes with it. You’re missing concave corners at the very least. In your example image, you’re using the solid brown tile as both all-ground and as a concave corner, but Tiled can only use each tile in a single scenario, it can’t use the same tile in multiple ways, unfortunately.)
Edit: I’ve written some notes on labelling terrains here, perhaps they’ll be useful. Perhaps it’ll help you understand the concepts behind terrains better, as the concepts are the same whether you’re doing top-down maps or side-scrollers.