Try these instructions for configuring your CA security suite...
PortForward.com - Free Help Setting up Your Router or Firewall
If you are using the full suite including the anti-virus protection it is wise to disable your Norton as having 2 will more than likely clash and give you less protection to no protection at all....
Your modem/router may also have an inbuilt Nat firewall, but I couldn't find any info on it at the port forwarding site....