if SG is not already installed, then yes, simply swinstall SG, and follow th procedures documented in the Managing Serviceguard at
http://docs.hp.com/en/ha under Serviceguard.
P.S. make sure you patch the system, especially teh correct PHSS* patch for the version of Serviceguard you are installing.
My house is the bank's, my money the wife's, But my opinions belong to me, not HP!