If the bird is amenable to coming out of the cage, let him or her stand at the threshold of the cage, right at the open door for a while, and then eventually trying training him or her, over a period of time, to step on to your hand. Maybe this bird has been held before and is already comfortable standing on your hand. But if the bird isn’t comfortable stepping up onto your hand, take a favorite food item and hand it to the bird through the cage bars, at first. Then let him or her stand at the open cage door threshold, and hand him or her a little treat. Ultimately hold the treat in your hand farther back, so that to get that treat, he or she needs to step onto your other open palm to reach the other hand that’s holding the treat. This is something that can take weeks to train a bird.