For example, if your Ragic server's domain name is ragic.example.com, you can assign an additional domain name called ragic-api.example.com and point this domain to the same IP as your Ragic server. This way ragic.example.com will serve the normal Ragic service, and ragic-api.example.com will serve the API content.
Also remember to restart your Ragic service after you change configurations here for it to take effect.