Previously I have shown the Openntpd setup on Gentoo, here's how you can quickly set it up on FreeBSD. Please do take note that this is more of ntp client type setup.
shell>pkg_add -vr openntpd
Configuring Openntpd by editing /usr/local/etc/ntpd.conf, just comment out the default ntp server and add the ntp server you want.
# sync to a single server
Add this one liner to /etc/rc.conf for it to run on system boot -
Start Openntpd manually now -