You can change ERSSD user paswords, add users, and assign permissions.
Both these commands alter the password at Replication Server as well as at ERSSD, and update the Replication Server configuration file.
For more information on these commands see the Replication Server Reference Manual.
To add a user at the ERSSD, use isql to access the ERSSD as the primary user and execute grant connect to username identified by password.
To give a user permission to read the Replication Server system tables, execute the command grant membership in group rs_systabgroup to username.
To grant sa privileges to a user, execute grant dba to username.