To Redistribute a loopback address with BGP:
Configure the BGP next hop Export to be use-self. Under Virtual Router > BGP > Peer Group > select the Export Next Hop to be use-self and Type to be 'IBGP'.
Configure the loopback IP address in the Redistribution Profile. Under Virtual Router > BGP > Redistribution Rules, type in the loopback address and set the origin to be 'Incomplete'.