Newbie Port Filter Question on 4.10stable

[Simon Fishley]

Hi All

Very new to FreeBSD and google has not proved helpful for once.  Running
4.10Stable and I would like to allow traffic on port 20 on my server and I
assumed /etc/rc.firewall was the place to do so. I added a line in the file
in the same format as the rule allowing port 21 traffic but was not sure how
to restart the firewall. #sh /etc/rc.firewall was a bad idea and totally
shutdown all traffic.

Can anyone point me to a clear resource on what I should do to start, stop
and flush the port filter rules and whether or not I was working in the
correct place to begin with.

Thanks in advance
Simon