how to add users to xmpp muc room with XMPPFramework library

how to add users to xmpp muc room with XMPPFramework library

I am creating group chat app. I am able to create the group with below code.
_xmppRoomStorage = [[XMPPRoomCoreDataStorage alloc]init];
XMPPJID *roomJID = [XMPPJID jidWithString:@"room1@conference.abc.biz"];
_xmppRoom =[[XMPPRoom alloc] initWithRoomStorage:_xmppRoomStorage
jid:roomJID];
[_xmppRoom activate:_xmppStream];
[_xmppRoom addDelegate:self delegateQueue:dispatch_get_main_queue()];
xmppRoom joinRoomUsingNickname:_userNameEdit.text history:nil];
but now I need to add some users to this group. Can any one please let me
know how to add or invite multiple users to this group.
I have one more problem. not able to create 2nd room when 1st group is
active. When I try to create 2nd room it gives below error
"XMPPRoom[room2@conference.abc.biz] - Cannot create/join room when already
creating/joining/joined"
Thanks. Vaz