Custom domain first steps: difficulty with URL path and Pages daemon

EDIT: It seems I am following the documentation for people hosting their own gitlab instance. I’ll update the topic properly when I’ve figured it out. But I’m trying to point my custom domain to my static pages on gitlab.com.

I’m using git on linux to commit and push to a gitlab repo (Pages). The repo is private but the page is public.

The documentation[1] for adding a custom domain says to " either external_http or external_https in /etc/gitlab/gitlab.rb to the IP and port of your Pages Daemon".
Where do I find this IP and port? I tried just pinging gitlab.io but that IP gives a 401 in the browser.

Another question: when I visit .gitlab.io, I am prompted to login rather that seeing the static site. But visiting .gitlab.io/ works. When I change the DNS for my domain name, aren’t people going to get the login prompt as well? If so, how can I remedy that for the custom domain?

1: Custom domains and SSL/TLS certificates | GitLab