Open up your terminal and install tigervnc via yum.
Type this command in your terminal:

yum -y install tigervnc tigervnc-server

Edit the VNC configuration file
vi /etc/sysconfig/vncservers

and append these lines:

VNCSERVERS="1:user"
VNCSERVERARGS[1]="-geometry 800x600 -depth 16"

Where VNCSERVERS= is for configuring the username.

The "1:user" tells the vnc server that the username user is map to display 1, so the port number to access this user via vnc is 5901.