Cluster installer can be downloaded from this page:
Look for deployment-14.12.tar link.
The warning about the directories means that all of the directories specified on the right side of options data-dir-prefix-X-Y must exist before the installation starts.
The requirements from the README files mean that you must have ssh connectivity from the default coordinator (first server listed in config.ini) to all of the other servers in the cluster. Cluster installer will be setting up password-less ssh access from the coordinator to all other servers. So, firewalls or anything that prevents unrestricted network access between the coordinator and the other servers has to be turned off prior to starting the installation.
The second statement in the README file states that the same user account with the exact same home directory must exist on all servers in the cluster. This is the account that will be used by scidb.