The psychologist who was the director of training or your direct supervisor (while you were completing your training) should complete the form. If the experience took place a number of years ago and the supervisors are no longer at the site of the internship, it is possible for the current director of training to complete the form based on institutional records. Signing the form involves attesting to the satisfactory completion of the internship requirements.  It is important that doctoral level psychologists attest to the competence of the doctoral intern.