Help to configure squid inside a lan

Hi

I need help to configure squid inside a lan. Proxy network address is
192.168.1.231 and firewall network address (lan) is 192.168.1.241. I use
fedora core 2 and squid release 2.4.STABLE5. For now, my firewall use only
one iptables instruction

iptables --table nat --append POSTROUTING --jump SNAT --to-source $WAN_IP

so it is really open to all!!!

How can I configure my squid.conf? I used

cache_peer myfirewall parent 80 0 0 default no-query
http_access allow myacllist

bat it does not work.

Thanks