Custom Domain setup

Hi, I am trying to use API in my domain. I am running the Tyk Dashboard using Docker. After the execution of setup file, it shows the portal to be www.tyk-portal-test.com/portal/ When I try to open my portal it doesn’t open. Should I use my hosting domain name, so that from which API could be accessed? In custom domain options, it shows me to save it to the dashboard settings file.
custom_domain
where should I save this?