Okay, before we even start messing with the Arduino, let's get the ID-12 wired up. Follow the wiring layout above using your breadboard and jumpers to make the necessary connections.
I did not show an LED connected to the LED pin (10), but it's a good idea to use this at first for read verification. Also, I prefer to insert a small capacitor (100nF) between +5V and ground to keep the power clean.
Once the ID-12 has been connected it's time to bring out the Arduino! Connect TX (D0, Pin 9) from the ID-12 to RX on the Arduino.