If you are using a XBee XSC S3B on our XBee Shield board, you must remove the RSSI status LED and put a 10Kohm Pull-UP resistor between the 3.3V and Din pin of XBee socket. If you have questions about this process, you can guide with the following example image.
This is an “easy-to use” USB unit to serial for the XBee line. This unit works with all XBee modules including Series 1 and Series 2.5, standard and Pro versions. Plug the unit into the XBee Explorer, attach a mini USB cable and you will have direct access to the serial and programming pins of the XBee unit.