How do I download Tunein Radio to a Mac?

The short answer is "you don't." There is no tune-in application that runs on the Mac (at least not from Tunein itself). You can use the web client without difficulty. Just log in to tuenin.com in your browser. There's no way to get anything like a miniplayer, though. Alternatively, you can use the iPhone app and sling the sound to an external device with AirPlay. If you want to sling to a computer, use something like Airparrot 2 or AirServer on your computer (which will make the computer show up as an AirPlay device on your phone).

It cannot be installed on the computer. Different platform, different operating systems. iDevice apps don't work on Macs and vice-versa.

You might search the app store. There may be a similar-functioning app for your mac that will accomplish the same result. 🙂

I don't have the app so I don't know what it offers. TuneIn has a website. Do they offer the same content/experience on their website?