Failover IP setup

I've bought a failover IP address but it's not clear to me on what I should do next.
It's pointing to my instance but what are the next steps to get it working? Pointing my domain name at that IP address doesn't seem to work so I assume extra steps are required.

I've seen a number of tutorials for adding network stuff to the instance but I'm not sure if that's what I should be doing as the files they're telling me to "edit" don't exist on my server, I'd be creating new ones. For instance, I've seen this article: https://docs.ovh.com/gb/en/public-cloud/configure_a_failover_ip_with_ubuntu/#_1