Look for VISA in labview. Its a library (or toolkit) which is for serial communication. U can send data to xbee from labview in two ways. One way uses arduino where labview sends data to arduino and arduino in return sends data to Din pin of xbee (which ultimately gets transfered to the receiving xbee).
The other way is quite simple, u can connect a ttl to usb on the Din, Dout and GND pin of ur xbee, (here no arduino is required for labview side xbee) and then use VISA toolkit to send data to xbee which gets transfered to receiving xbee.