HowTo setup Multicast on PC 5548

Can anyone suggest a HowTo or walkthrough for multicast (IPTV) setup on a Powerconnect 5548 switch or similar?

I have been reading and researching extensively but cannot get my head around the concept.
I found a snippett here: http://en.community.dell.com/support-forums/network-switches/f/866/t/18937808.aspx

Quote: "it takes a unique identifier for a type of traffic as defined by RFC 1430 and when applied will map this traffic type to a particular VLAN"

There is plenty of information in the manual but it is very confusing so a hypothetical example would be greatly appreciated.

Thanks in advance.