How to use Height Maps

Sounds so simple in the manual but exactly how do I import a height map, nothing seems to work for me.

One of my students just finished a series of video tutorials on creating Unity terrains. One of the chapters is on creating and importing Height maps:

Hope this can be of some help!

Have you seen this question and answer:

There's some good advice there. If none of that solves your problem, you'll need to add a bit more detail to your question - such as, what app are you exporting your heightmap from. What size image, what are your terrain settings, etc.