Local Firewall

Hi everyone,
I have two windows computers and one freebsd computer.
I want to establish data communication between these two windows computers through the FreeBSD installed device.
PC1 = Windows Pc1, PC2 = Windows PC2 and FirewallPc = computer with FreeBSD installed.
There are two adapters on Firewall Pc. Fxp0 and re0.
PC1 connected to FXP0. Pc2 is connected to re0.
How can I send the packetI sent from PC1 to PC2 via FirewallPc?
FxP0 needs to send packet from PC1 to re0. And re0 will get the packet from FxP0 to PC2.
This has nothing to do with firewalling, it's just plain old routing.