Let me be clear, I am not saying anyone should use the ipcc file, mms was working fine for me, out of the box with beta 2. I applied it, just to see if it still worked and it did, it unlocks the two settings menus, and mms still works for me, as of a couple minutes ago.
Now, should you choose to use the ipcc file, you can apply it by choosing shift+click (option + click on a mac) browsing to the file (change file type to ipcc in the file browser) and iTunes will install the carrier update for you.
I am not convinced it is necessary for this version of the beta however mms did not start working for me until I applied it on beta 1. Use it at your own risk.