Firebase - How to set up a white server for production servers?

I have a problem with an app server that I am using to send notifications using the Firebase HTTP protocol.

The implementation on my development app server is working, so apparently all I have to do is whitelist my IP app server and I'm good to go.

However, I cannot for the rest of my life learn how to do this through the Firebase Console. All the references I have found are for the old console layout, so I am at a loss.

Any help would be greatly appreciated.