The manuals were very slim on the subject.
"If you want to hear 5.1 CH audio, connect the digital audio out jack from your
DVD / Blu-ray player / cable box / STB satellite receiver directly to an amplifier or home theater."
OK, I get that but the ONLY OTHER IDEA I could glean was to tap the MTS button on the remote. Beyond that, I'd call it in. 1800SAMSUNG in the USA.