Cole decides,"being invisible had nothing to do with being seen. What did Cole need to do to be invisible?

In Chapter Twenty-Three, Cole realizes that in order to be invisible, he must be able to clear his mind.

TO BE INVISIBLE he had to clear his mind. That was the secret. Cole stared up into the darkness. In the cold pond, his mind became almost trancelike. The fish and the beaver had come close until he thought of hurting them . The day he touched the Spirit Bear he had been near death and had completely given up trying to be in control. Being invisible had nothing to do with being seen. Being invisible meant not being sensed or felt.