I have been certified by the International Harp Therapy Program (IHTP) since 2014. The IHTP is accredited by the National Standards Board for Therapeutic Musicians (NSBTM). The NSBTM has a directory of therapeutic musicians worldwide as a part of the Institute for Healing through Sound and Music. My entry in that directory is here.
I use two harps in my practice: a fully levered 27-string "Jessie Nightingale" harp by Jeff Lewis of Lewis Creek Instruments and a 34-string Crescendo model built by Dusty Strings) in Seattle. I have a set of these instruments in Hawaii and in Michigan.
The links on the left provide explanations and examples of the skills needed to do this work.