Set up is important. But the base key is you pause the TV exactly at a whistle and you play the radio broadcast and as soon as you hear that whistle you unpause the TV. It’s not perfect by any means due to commercial slippage but it will get you set up.
I run the game on the TV and have my phone(or computer) streaming the radio broadcast through my speakers. But I have a separate mixer running the whole thing. External speaker will work in a pinch. The key is finding that “clap” aka whistle in both broadcasts.
So the starting whistle is the easiest because you know it’s coming and you can pause it almost exactly. Radio is usually half a minute behind broadcast so.