Does anyone know how to tame a cockatiel?

[Gumby the gelding]

Hi! Does anyone know how to tame a cockatiel? Mine is scared of people. It eats millet out of my hand and goes on my hand to eat food and does step up sometimes. It’s on my hand in the pictures but goes away from my hand, but when it does that I take my hand out and try again.

 

[Gumby the gelding]

It’s not actually that scared!it sat on my hand eating treats for 50 minutes, but still goes away sometimes.