This is a base service so all you need is a few rc.conf vars Download this conf and add it to /etc/rc.conf.d and run service ipfw start
firewall_enable="YES" firewall_type="WORKSTATION" 4 firewall_trusted="xx.xx.xx.xx" 1 firewall_myservices="22/tcp 53/tcp 53/udp 80/tcp 443/tcp 20/tcp 21/tcp 1984/tcp 25/tcp 143/tcp 993/tcp" 2 firewall_allowservices="any" 3
sysrc blacklistd_enable="YES" touch /etc/ipfw-blacklist.rc vim /etc/blacklistd.conf #edit the default and add some whitelists for IP's
Basic firewall using IPFW
I don't use PF on FreeBSD as it lacks a lot of features from OpenBSD and I believe each OS should stick to it's own firewall and either add in options to it, we really dont need 3 firewall's in a OS. Each firewall has it's pros and cons.