Bind Vpn-Client Connection to local Interface

[lo0l]

Hello,
i have set up opnsense, my setup is a computer with a 4 port network adapter.
one is WAN(0), other is LAN(1) and the third one is connected to a wifi Router(2),
i have a vpn client connection running, now I want to bring all traffic from Router(2)
through the VPN Tunnel an nothing else, what is the best way to do that?
Thanks a lot, Ive played with the NAt settings but it didnt worked.