how to start ,configure vncserver on linux?

You will need several things to get started:

log in by root

start the vncserver simply invoke the following commands:

[root@roswell etc]# service vncserver stop
[root@roswell etc]# service vncserver start
Starting VNC server:                                       [  OK  ]
[root@roswell etc]# 
[root@roswell etc]# vncpasswd

su orale

[oracle@roswell etc]#
[oracle@roswell etc]# vncserver :2

New 'roswell:2 (oracle)' desktop is roswell:2

Starting applications specified in /home/oracle/.vnc/xstartup
Log file is /home/oracle/.vnc/roswell:1.log

[root@roswell etc]# 

got to the xstartup file and make the following changes

vi /home/oracle/.vnc/xstartup

uncomment the first 2 lines and replace twl with startx

vncserver -kill :2    kill session 
vncserver :2          start session