The infra-red receiver is a simple device with three pins - two for power, and one for data. Using this device you can receive infra-red signals, as produced by simple remote-controls.
Pins are, left to right, when looking at the receiver from the front:
- Sensor Data
- Ground
- Vcc
The infra-red receiver can be controlled via the standard IRremote library, but note that this is a blocking library.
If you wish to perform other, non-blocking operations, such as reading the temperature, you'll need to use an interrupt-drive library - and this means you'll need to wire your data-line to the digital pin 2 or 3 (if you're using the MP3 shield pin 3 is unused :).
I've found that the IRremoteNEC library is useful for this non-blocking operation.
Wire up an Infra-Red receiver, and write code to display the buttons you've pressed on the screen.