Suricata, Zenarmor , interfaces and vpn

[Monju0525]

I am currently using a vpn via Wireguard. It works great.
Zenarmor is assigned to the lan. What should Suricata (IDS)  be assigned to : the wan or the wireguard_interface?
Under the IDS advanced mode, do I need to modify home networks? The helps says  "Networks to interpret as local", what does that mean?