2d platformer in-editor tutorial problems

Following the path on getting started, I got to the part where you must explore a minigame. I chose the platformer and started following the steps. When i got to the part where you need to drag an enemy prefab onto the level, the prefabs area was entirely 'greyed out', as were all the folders. Nothing could be clicked, dragged or selected in any way.

I got around this by duplicating an existing enemy from the hierarchy window and then deleted it. Once I did this, the ENTIRE WINDOW of the unity editor became the same dark blue 'greyed out' and I was unable to touch anything in the project at all in any way. I simply had to close Unity. This happened twice, and I am not sure why! What am I doing wrong?

 

Can you post a screen shot?