The easiest way to make a T-Splines model is to make a primitive. Primitives are simple shapes like boxes, planes, cones, and cylinders. You can find a list of T-Splines primitives in the drop down menu. There are also icons for the T-Splines primitives. You can find them by clicking and holding on the Create icon, then the primitive box icon, and then the whole primitive toolbar will pop out. To make a primitive, just click on the icon, then follow the prompts in the command line.