Art therapists work in a variety of settings including hospitals, counseling clinics, schools, and private practice. The specific job will depend on the level of training and expertise. The basic job involves using art to elicit feelings and emotions that can then be explored to reach counseling objectives. The types of art used include drawing, sculpture, painting and other self expression forms.
The American Art Therapy Association link is at http://www.arttherapy.org and there you can find a lot more information about the field and jobs.