1 install vnc server

yum install tigervnc-server

2 add vnc user

useradd vic
passwd vic #change password

3 make config file for the specific user

cp /lib/systemd/system/vncserver@.service /etc/systemd/system/vncserver@:1.service

edit the config file 

vim /etc/systemd/system/vncserver@:1.service

content of the config file should be 

[Service]
Type=forking
# Clean any existing files in /tmp/.X11-unix environment
ExecStartPre=/bin/sh -c '/usr/bin/vncserver -kill %i > /dev/null 2>&1 || :'
ExecStart=/sbin/runuser -l vic -c "/usr/bin/vncserver %i"
PIDFile=/home/vic/.vnc/%H%i.pid
ExecStop=/bin/sh -c '/usr/bin/vncserver -kill %i > /dev/null 2>&1 || :'

4 change filewall settings

firewall-cmd --permanent --zone=public --add-service vnc-server
firewall-cmd --reload

5 start the vac server as the specific user

su - srijan
vncserver

6 make vnc server start during boot time

su -
systemctl daemon-reload
 
systemctl enable vncserver@:1.service
 
reboot
systemctl start vncserver@:1.service