I've added a service via a public docker image; adminer. The service has a private url to communicate, but how do I set to communicate to the right port?

For reference, locally, I bind the 8080 port when I spin up the container, which is were adminer talks to. But on production, how can another one of my services communicate to ${{RAILWAY_PRIVATE_DOMAIN}}:8080 ? I can't find an option there.

Do I need manually create an image that does the expose inside the image itself?