What are ways to train a cockatoo to step up?
I have tried offering my hand and say step up (I show her the treat) but she just ignores the hand
and I also tried clicker training.
It takes time, especially if this bird has never had much interaction before. Be patient, talk to him, read to him, sing to him, whatever you want...When he starts taking treats from your hand, try putting your other arm/hand in-front of the hand holding the treat so that he has to lean over to grab it. Every day gradually make him lean over more and more until he eventually has to step up to get the treat.
This could take weeks or even months, be patient and eventually he will step up.