After I have made Game objects, they appear as black voids with no discernable edges whatsoever. How do I change this so I can see the lines in the cube or other geometric objects, not just the dimensionless mass?
It sounds like you have a shader issue, or a lighting issue. Make sure you have a shader like diffuse set in your material block. If that does not do it add a light, anyone will work, but a directional light will guarantee light is shining on the object.
If both those don't work, maybe your normals are inside out. In your modeler, flip the normals and that might solve your problem.