An ideal situation for an advisor change is one where both student and faculty agree that an advisor change would be best for both parties. If you are able to discuss this with your advisor without feeling anxious or threatened, please do so. Work with them to find a new advisor and talk with the new faculty member about their willingness to serve in that role. If an agreement is reached, notify the DGS about your plan.
However, should the situation be uncomfortable and you feel you cannot talk to your current advisor without feeling anxious or threatened, please make an appointment with the Director of Graduate Studies, who will listen to your request and work with you to develop a plan.