Via BluRay players with apps: your blue ray player should have analog outs, you would simply need to install a cable from the analog outs on the player to the corresponding input on your a/v receiver.
Via Smart TV's: Some smart TV's do not have analog outs, only digital, if you only have optical available you cannot get Pandora in Zone2. There may be an 1/8" mini jack audio out though, if you have one of these you will need a cable that has 1/8" mini jack on one end and rca's on the other, then you can plug the RCA's into the receiver to get internet audio on Zone2.
Via Apple TV: Apple TV only has Digital outs, there is no work around to get audio on Zone2 (AppleTV doesn't have Pandora right now anyways).
Via Roku: Most Roku's come with a supplied break out cable (1/8" mini jack to three RCAs - composite video, and audio). You would simply install the breakout cable & route just the audio jacks to the same input on your receiver.
Via Sonos: Sonos has it all figured out, you should easily get Pandora on your Zone2, no work around needed! yay.
If you use any of the above work arounds, remember that the analog audio needs to be plugged into the same input on your receiver, for example if you have pandora on your blue ray player, and the blue ray is using input one on your receiver, then the analog audio needs to be plugged into input one. That way if you have independent zone source switching, everything will be correct.
I cannot give much insight into the settings of the reciever, as everyone will have a different a/v reciever.