It takes some time. I think you'll find he develops a more relaxed, confident demeanor as he gets older. Patience and consistency are good things to practice (and can be hard when you first get one!).

As long as he's eating and doesn't seem too stressed out, I would recommend holding him for short sessions (5 to 20mins) 3 to 5 times a week.

My experience is that very slow and steady hand motions help alot. Also, getting him out of the cage gently helps get a handling session off to a good start. A good handling session would be one where the snake is happy to sit fairly still.