The tutorial is pretty unclear and I think this is impossible if you (like me) don't have numpad on your keyboard. Interesting idea with a little less stellar execution.
Viewing post in Rotation is optional jam comments
Yeah, to be honest it was more of a screw this rotation business I am going to finish the game before the deadline. But the numpad issue is a valid point. Thinking about it I should have put the rotation on the arrow keys and q and e or made an option for that, since Unity's system input package supports runtime changes.
Anyway, sorry you had to endure it. Got to improve my coding and quaternion skills a lot more.