To play dvds you need to have some pieces of software installed: libdvdcss and id-my-disc. you can install them from the video wizard / add software section, or by hand in a console:
apt-get install libdvdcss
apt-get install id-my-disc
sometimes, the installation from the wizard fails, so it' s better to try the other way. Then , you will be able to play your dvds.
your media is discovered if it is shared over the network. The internal network is automatically scanned for shares from time to time and you will be asked to add your shares when they are detected. If they are not detected automatically, you can try to add them manually. See these links also:http://wiki.linuxmce.com/index.php/Howto:_Using_Network_Shareshttp://forum.linuxmce.com/index.php?topic=1347.0