Vertebra Segmentation

Operating system: Mac
Slicer version: 4.10.2
Expected behavior: I am trying to segment the vertebra into individual vertebrae. The 3D slicer allows me to threshold relatively easily and isolate the backbone. However, the grow from seeds function does not appear to work. I am not able to place and identify seeds. The same problem occurs for simple region growing segmentation. Do you have any tips?

Basically, does anyone know how to create AND place seeds? It never lets me place them

Check out these turorials:

Several of those uses “Grow from seeds” effect.