Download ETS2 Local Radio from the releases page
Extract it wherever you like
Execute ETS2 Local Radio server.exe
Click the “Install plugin for Euro Truck Simulator/American Truck Simulator” button.
Open ETS2 Local Radio (or go to http://localhost:8330) and have fun.
Additionally, you may want to look at the web/config.js file and set some additional settings to make the make your experience even better. Please make sure that the keys and buttons you assign in ETS2 Local Radio are not assigned in game as well.

Make a station favourite to always switch to that station when entering the country it’s located in.

You could add the streams from the \web\stations\stations-america.js file to your live_streams.sii file if you wanted to, but then you would not get the spatial awareness, as all streams would always be available. I am not 100% sure that all streams will work though, because I’m not quite sure what stream types are supported natively by ATS.