The Structure > Objects > Walls node defines the walls that you want to add to your catalog and hence to your model.
Before defining walls, you must define the layers that you plan to use to compose your walls in the Layers node.
After defining your layers, you define the compositions of your walls in the Wall Composition node, see Define New Wall Composition Part. When the compositions are defined, you can then define your walls in the Wall General node, see Define New Wall General Part.