Hello everyone. I'm newbie with RME's products and TotalMix seems to be too hard for understand

Please tell me, how to activate Talkback function? I studied manual, but nothing became clear for me, and there is no tutorials on Youtube. I need step-by-step tutorial.

So, I have a mic in control room to talk with singers. What should I set up in Total Mix's preferences? When I press Talkback button on ARC controller nothing happens, even no light.