NCF – Extended list of Neutral creatures.

Okay... I think I did everything as instructed, but I can't create or edit units (the game just starts)... Can you tell me how to do it correctly?

To improve and create new units, you need special programs and a lot of knowledge about scripts. NCF simply adds things that weren't there before; it's just an addition to the game and doesn't introduce anything new for creating or improving existing units.