should i configure the two xbee modules before i'm using it?
Only if you want them to talk to each other.
and can some one tell me how to configure it under linux OS (fedora 20).
Install Wine and some version of Windows. Then, use X-CTU. Or find a friend that has Windoze.
because i haven't windows now and this task must be delivery to my prof after 10 hours from now.
Sorry to say, but you are screwed.