Add a Port to Virtual Host

CentOS Linux 7.9.2009
Good Morning.

I am working on an application that is installed on a local network. When a new user is created an API call is made to a remote application that is public facing. Both application are on Virtualmin. I would like the remote application to consume the API from a specific port - then lock down that port to the IP of the local network.

The remote API application will still need the ability to log users in over port 80. I see the virtualhost has port 80 assigned to it and 443. How can I add an additional Port?

Any help would be appreciated.