Here's the link to get the detailed instructions.
Note: It is recommended that you use the Unicast messaging type. Unicast requires less network configuration than multicast.
Thanks Vijaya and Ahmed,
i have changed weblogic messaging mode to multicasting following your steps.
There is one Multicasting test one can perform before going for multicasting, this test will ensure that the multicast ip and port are free and only managed servers in your cluster is listening to that ip and port.