Setting up high-availability failover mode in GCP

[phishing_hero]

I have written a terraform script for GCP to set up OpenVPN failover using this documentation(https://openvpn.net/vpn-server-resource ... over-mode/). It says to set up one "shared virtual IP". I have created 2 instances of OpenVPN but from GUI I am confused about what should be the "Shared virtual IP address". Can anyone elaborate on it? I do not see any option to set this IP in GCP. So far I have found https://cloud.google.com/solutions/best ... -addresses but I do not think this is what I am looking for.

PS: I have public IP and private IP for both instances.