How do I get my autistic adult brother(23) into an adult dy program and what are some good one in houston?

I have a younger brother and I want to put him into an adult day care center during the day. Some place that can pick him up and drop him off. He has united healthcare community plan, TXMMP plan. Medicaid and medicare together i want to see if his Insurance need to get a prior authorization form from his doctor. What should I tell his doctor? How do I go about this?