The first thing you need to understand when modeling with T-Splines is the concept of control points. T-Splines surfaces, just like NURBS surfaces and curves, are defined by control points. When modeling with NURBS surfaces (Rhino's main type of surfaces) most of the time you don't use the control points, or might not even know that they are there, but 90% of modeling in T-Splines is comprised of moving control points. It's very important to understand the basics of how they define the shape of your model.