You need to install the vnc server package on your redhat machine.
then get the vncviewer for the other machine here: http://www.realvnc.com/download.html
or from you distro install cds
and install it on the client machine.
you can just start vncserver on the remote machine without any options (default)
"vncserver -h" should help you along further
connect to the remote machine with "vncviewer" enter server ip:1 in the dialog that pops up and click o.k.
and you should atleast be on your way.