To enable SSH access for the root user you need to have another user created through ViClient.
After you are logged in SSH session with that user, switch to the root user with the command:
Edit the configuration file for SSH with the command:
Find the line that starts with PermitRootLogin and change the no to yes. You can find this line about 2 pages down from the top. Save the file by first pressing Ctrl-O and then Enter. Exit with Ctrl-X.
Restart the sshd service with the command:
service sshd restart
You should be good to go!