MyBB Community Forums

I have tried putting java chat app html code in header of current theme. and It is working but It is not what I want. I want a separate tab of Chatroom application by http://www.addonchat.com/ where I can put html code not in header and footer. It is disturbing chatting experience whenever I open some link of forum in new tab. header and footer is good for advertising things only not for java chatroom.
Help.

you can make a separate page for the chat room and use a top link for it

see PageManager plugin (see also its reviews) for a simple method to add separate pages

see also adding / editing top links