How to setup Media Server to use iTunes Database on WHS2011

Hi guys,
Trying to reorganise my music collection, and as I already use itunes for my iphone, ipod, ipad etc, I want to try and keep one music databse up to date, and use itunes for Music Server. I thought I had set it up correctly, but it seems to have duplicated all music. Can anyone show me a guide on how to set it up correctly?

thanks in advance...

Nick