The documentation talks about getting the built in feed url from Octopus from the Library -> Packages page: https://octopus.com/docs/packaging-applications/package-repositories/pushing-packages-to-the-built-in-repository
Unfortunately the “show examples” link does not exist until at least 1 package has been uploaded to the server.
I’ve already done this myself so it’s not an issue for me anymore but I’m sure this will be an issue for another customer in the future.