Counselors set up their own accounts at: https://app.benefitkitchen.com/agency/signup. There they should click the “Caseworker” option, select “I work for an agency”, and fill in their “work” email address and preferred password (counselors should make this something memorable and write it down).
After they have signed up they will be given an Account Number and PIN (it will appear on screen and they'll get an email). The counselor should write these down and give them to their agency administrator. The agency admin will connect the counselor's account to the agency via the agency administrator interface.