Looking at the files included in the shorewall-4.5.4-1.fc16.noarch.rpm package on koji, I see /lib/systemd/system/shorewall.service. In that case you would start the shorewall service at boot with:
# systemctl enable shorewall.service
Or do an immediate start with:
# systemctl start shorewall.service
Beginning with F15, most services have been converted to the systemd system, with only had small handful of services running under the old SysVInit system.