The illustration shows just some of the bone structures that are usually visible unless hidden by hair or fat. It's much harder to spot these landmarks on a child's head, for the masses of fatty areas. But you shouldn't have a problem finding these areas on an adult head. Next time you're on public transport, see if you can spot any. Wear sunglasses so people don't think you're a weirdo. Some heads are fascinating to the artist, because of pronounced features. Every skull is different, so draw many different skulls to develop your practice.
It's interesting to look at a map of the skull and feel around your own head for these landmarks. Do this as you draw the head from multiple angles and you'll have these landmarks committed to memory.