The Arduino Wireless shield allows your Arduino board to communicate wirelessly using Zigbee. This documentation describes the use of the shield with the XBee 802.15.4 module (sometimes called “Series 1” to distinguish them from the Series 2 modules, although “Series 1” doesn’t appear in the official name or product description).
A Simple Example
You should be able to get two Arduino boards with Wireless shields talking to each other without any configuration, using just the standard Arduino serial commands (described in the reference).
To upload a sketch to an Arduino board with a Wireless shield, remove the Xbee. Then, you can upload a sketch normally from the Arduino environment. In this case, upload the Communication | Physical Pixel sketch to one of the boards.
Read more: Arduino and Xbee wireless setup