How do I create a 3d model from a height map?

I saw some tutorials on how to do this, but none of them started at the beginning, plus I’m new to using blender, so most of the directions are confusing and don’t make sense to me. I’d also like some help creating a heightmap from an image?

Which part is missing?
Here is one which would i consider as complete:

Heightmap tutorial:
For the height you use the grayscale map, later on you could color it with the finished texture.