Dubbin
Before you try to port forward your router, please check that you have got UPnP enabled on the following.
a) Your Windows O/S
b) Frostwire
c) Your Router
d) Your Modem
If all the above have UPnP enabled then your Frostwire should work if, however, it still shows the brick wall then you will have to try port forwarding as a last resort.
Here is the URL leading to the instructions on how to port forward your router.
PortForward.com - Port Forwarding Limewire on the Netgear WGR614v9
UK Bob
PS. The Port Fowarding people also have an application called "PFConfg" which will automatically port forward your router, you may want to get this (it cost $29.95). I've never used this app so cannot vouch for it.
PPS. The above URL leads to port forwarding your router with Limewire, I could not find any instructions specifically for Frostwire.