Hi Sreenivas,
You need to contact your Security/Basis team to assign this perticular role to your user.
Once the role is assigned then you would be able to access this option in your channel.
http://help.sap.com/saphelp_nwposc/helpdata/en/b6/883e46939c42298f55fecdcd618d6e/frameset.htm
http://help.sap.com/saphelp_nwposc/helpdata/en/2e/99f0fb5a9e45b3b148c90e87fafcd1/content.htm
http://help.sap.com/saphelp_nwposc/helpdata/en/1a/71c26a6faf40428d7fdea9f088cdc4/content.htm
Thanks,
Naveen