Fio + XBee library for point-to-multipoint network

Hello. I'm trying to set up a network of several Fio boards to communicate wirelessly with Firefly for Grasshopper. What I'd like to do is have the Arduino get an address for the on-board XBee, have Firefly "read" that address and select the correct values to send to each Fio based on the associated address (it will be transmitting to 8 Fios). This seems like it should be fairly straightforward using the XBee library, but I'm not sure how having the XBee on board as opposed to connected via a shield affects how to get the address. The RX/TX pins of the XBee are, I believe, already connected directly to the RX/TX digital pins of the AtMega, do I still need to set up a soft serial port? I'm pretty hazy on a lot of this wireless communication stuff, so any help or advice would be greatly appreciated.