Hi
If you only need to multicast on a single vlan then if your switch supports it you can do the following
1) Turn on IGMP snooping. You will have to do this anyway. "ip igmp snooping".
2) If your switch supports it you can then also make it an "igmp querier".
This would be enough for it to work.
If your switch doesn't support "igmp querier" you need to add under the router interface connected to the LAN
router(config-if)# ip pim dense-mode
Note that you will still need to turn on IGMP snooping on your switch.
If your switch doesn't support IGMP snooping then you should use CGMP.
HTH
Jon