SLES 12 sp4 vncserver

I tried to setup vncserver using vncmanager and when I connect using vncviewer I get a message that the connection is not encrypted. I would appreciate guidance on how to do this. The online documentation is a little vague on how to edit vnc settings as there appears to be two files that might be edited. The first is /etc/xinetd.d/vnc and the second is /etc/vnc/vncmanager.conf
If I uncomment a line with encryption options (TLS, X509, None) in vncmanager.conf, vncviewer tells me that it cannot connect due to old encryption - or something similar.

I would appreciate some guidance on how to ensure that the vnc connection is secure and encrypted.