If you are looking for radio as per the title, then you won't find it on the TV channel audio choices, you will have to switch your receiver to Radio mode, it may be a single button, or may be a choice when viewing the channel list. It is not like the old analogue days, where one channel would carry unrelated audio bands.
If you are simply looking for different language versions of the channel you are watching, then as mentioned above, just press the audio or language button.