Create a plot plan polyline by imputing distance and angles into the New CAD Line dialog, then convert the polyline into a terrain perimeter.
Before you can use the terrain tools to create terrain objects, you must add a terrain perimeter to the drawing, and then be on that floor to add terrain objects.
Saving your houses or other structures as 3D symbols allows you to place multiple buildings in a single plan to create 3D views of an entire neighborhood, subdivision, or lot with multiple structures.