File transfer in group chat with XMPP

I am using group chat with openfire (MUC).

i can able to send messages but how to send file to group with Smack library.

i can able to send file to single user  but i don't know how to send file to group chat (MUC) so all users in room will receive that file.

someone told me that use XEP-0066: Out of Band Data but he didn't told me how can use this.

Please Help.