This is directly from page 39 of the manual.
A user can update their application using the bootloader in a wired configuration with the following
a. Plug XBee programmable module into a suitable serial port on a PC.
b. Open a hyperterminal (or similar dumb terminal
application) session with 115200 baud, no par-
ity, and 8 data bits
with one stop bit.
c. Hit Enter to display the bootloader menu.
d. Hit the "F" key to initia
te a wired firmware update.
e. A series of "C" charac
ters Will be displayed within the hyperterminal window. At this point,
select the "transfer->send file
" menu item. Select the desire
d flat binary output file.
f. Select "Xmodem" as the protocol.
g. Click "Send" on the "Send File
" dialog. The file will
be downloaded to the XBee Programmable
module. Upon a successful update, the bootloader
will jump to the newly loaded application.