The show is on live Sunday nights from 9 - 11 pm (US Central Standard Time). To listen, go to 897theriver.com and click the "Live Audio Listen Now" button. If you have Windows, it will open your media player. If you have a Mac, you need to do one additional thing.
You need to install Flip4Mac by going here: http://www.microsoft.com/windows/windowsmedia/player/wmcomponents.mspx. The link that says “Download Windows Media® Components for QuickTime” will take you to a download page. Download and install.
Now you have no excuse to miss the show. I assume you can figure out how time zones work and know when the show airs for your time.