On your Ragic server, there is a configuration file in conf/ragic.properties. Inside the configuration file, there is a configuration called "API_URL". You should put down a domain name or an IP to this server that you plan to use with your API.
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.