how to configure ntp

Really it's as simple as adding the time server to /etc/ntp.conf and to /etc/ntp/step-tickers:

/etc/ntp.conf:

server 192.168.0.5
server 192.168.0.6


/etc/ntp/step-tickers
192.168.0.5
192.168.0.6


Then of course make sure that ntp will start at boot time:
chkconfig --level 2345 ntpd on
chkconfig --list ntpd

And let's start the service now:
service ntpd start