Package ntp you probably have in your distribution. Older version have named xntp. You need programs ntpdate which is used for a single set date and (x)ntp for synchronization time for all time of system running. Ntp daemon has /etc/ntpd.conf configuration file.
In file /etc/ntp.conf should be contained next lines.
server 127.127.1.0 fudge 127.127.1.0 stratum 10 - Using local time if not present master time server.
If you can then use time server from the Internet.If you can then use time server from the Internet.
server tik.cesnet.cz server tak.cesnet.cz
The slave computers will have in configure file address master computer.
Next items you have on default setting.
driftfile /etc/ntp/drift multicastclient broadcastdelay authenticate no
If different between times on computers are highest than few second is better set to clock by ntpdate program if computer boots. This case is possible to use witting master computer address to file /etc/ntp/step-tickers or write command ntpdate <master> on end of /etc/local file.
Hint: ntpd synchronize time after several minute, sometimes you'll have to very patient.