According to the American Art Therapy Association, "art therapy is an integrative mental health and human services profession that enriches the lives of individuals, families, and communities through active art-making, creative process, applied psychological theory, and human experience within a psychotherapeutic relationship."
Art therapy is for anyone who is open to creative experiences. You don't have to be an artist to engage in art therapy; there is no age requirement nor talent requirement. All that is needed is a willingness to try something new. Art therapy is used in a variety of settings with numerous populations of people.
Well, that is really up to you. Art therapy isn't just coloring books and crafts. Just as there are infinite ways of expressing oneself, there are infinite ways of conducting art therapy. Sessions could include such things as drawing, painting, sewing, collage, working with modeling clay, and much more.