I have figured out the answer myself. I didn't click on a sprite within the Data menu before looking for the Prefab feature. You MUST click on a image before anything will appear.
I was following the tutorial on tilemaps and I noticed the easy prefab override option available...or what is suppose to be available? I don't see the Prefab option in the Data section of the 2DTK Tilemap script. I have included a picture of what is suppose to show, but doesn't.