Not confident, I asked daughter Tessa and son Ethan for help. Tessa arrived first, got BTN+ on her phone, then used some app to transmit it to the TV just in time for the first serve. I pursued my own path, without a phone, and later, that worked too. Ethan showed up to watch.
Readers GH and MC also reported success; GH went through ROKU and MC got her cable guy to come out and do it for her.