How do I make a 3D surface model?

The first thing to do is to segment the 3D surface that you are interested in. Click Editor, then click Effects. Your choices for segmentation here are Draw or Threshold, and also morphological operations (erode, dilate). To Draw, for example, click Draw and trace the structure in a slice, then click Apply and proceed to the next slice. To Threshold your structure instead, click Threshold.

Once you have made a segmentation (its name in Slicer will probably be "Working" unless you changed the default name), then click ModelMaker. Select the Working volume to make the model from, and then click Create to make the model.

After a little while, your model will be created and visible in the 3D window. To save the model, click ModelMaker, then Save.