How can I plot surface normals?

I am using the PDE toolbox to import a geometry and plot it. I now need to obtain the surface normals of that geometry, but I can't seem to do it. I have tried surfnorm and quiver, but it doesn't lead me anywhere. I don't know what I'm doing wrong. Any ideas?

[darova]

surfnorm needs surface object. Can you interpolate your data to create surface?

[Jaime Castiblanques]

The object I am importing is a surface, so I assumed that would do it.