Use xbees (series 2) to control a motor

Step 5: Connect the Xbee to the arduino.

Leave one xbee connected to the computer via the Xbee Explorer and the USB. The other xbee needs four connections: power (3.3 V), ground, tx, and rx. 

See the pinout in the image : the pins you have to wire are:
xbee pin 1: to Arduino's 3.3V 
xbee pin 2: to Arduino Rx (digital pin 0)
xbee pin 3: to Arduino Tx (digital pin 1)
xbee pin 10: to Arduino ground

You can also get an xbee shield like this.