Help with configuration

Hello list!

Im totally new with m0n0wall but have my router up and running.
Its a WRAP with 3 interfaces (sis0 = LAN, sis1 = OPT1, sis2 = WAN).
I also have a minipci wireless network card attached, so 
wi0 = OPT2.

And I want to configure it as follows:

I have two computers that I want to connect with ethernet. I thought
of having them connected to two different interfaces, LAN and OPT1.
I also have two laptops which to connect to OPT2.

So WAN and LAN is up and running, thats why Im able to send this mail :)
But the computer which is connected to OPT1 is not responding. Its a server
and therefor I thought of having it on an own interface. But how am I supposed
to configure this? I would like every computer to communicate to each other.
My initial thought is to bridge LAN OPT1 and OPT2 but its only possible
to bridge one interface to another.
Hope you understand me, ask anything otherwise!

Help please :)

Best Regards,
Patrik