Well, first of all, you need to understand that IPB is not a free forum software. You have to pay for a license in order to install your own IPB forum. If you would like to pay their licensing fees, then I would suggest going
straight to the source and asking for support.
There are, however, quite a few free forum software packages available to you.
Click me
Personally, I recommend YaBB (which is the first one listed there), but everyone has their own preferences.