As well as using an analogue input pin you need to bias it to 2.5V with a couple of 10K resistors, and then AC couple into that with your audio source.
But what are you trying to do, a Uno is barely fast enough for mono, let alone stero. The maximum sample rate you will get with that sort of setup is a 10K sample rate which is about telephone quality.
We you do get it working the numbers you get will look just like random numbers. The slow serial baud rate you use will also slow you down tremendously.