Pi Audio Injector for Music Box settings

When the Pi starts the MusicBox image I see the Audio Injector load.
I select the Audio Injector Stereo on the MusicBox browser settings page.
Playing music into Injector audio inputs, volume knob is turned up.
Tried selecting “Now Playing” or “Steams” from browser.
(not sure what to enter for the “URI” in the Streams page)
Not getting any music through the browser.
Don’t know what else to try.

I don’t understand this sentence. Does this card have a line in? Pi musicbox doesn’t support that. Pi musicbox outputs audio from local music files, streaming services, Web radio etc.

You understand correctly. Yes, the audio board has inputs. I guess I’ll just put music on the SD card then. I was hoping to create a “silent DJ” server through the Pi.

How do you normally play audio through the inputs with that board? Does it appear as an ALSA recording device which is then routed to the default output? How do you normally switch between the inputs and regular playback?

I just bought it with the hope that Music Box would work with it. I haven’t used it in any other way.