The same way it's taught if you go to music school. Practice. Have music played to you, and write it down. Start with very short pitch sequences; this will requ

The same way it's taught if you go to music school. Practice. Have music played to you, and write it down. Start with very short pitch sequences; this will require you, of course, to learn to recognize intervals accurately. Then move on to longer and more complex sequences. Lather, rinse, repeat.