The format is as follows:
https://ICS_HOST:ICS_SSL_PORT/icsapis/agent/oauth/callback
For example, suppose this is the URL you use to access your Oracle Integration Cloud Service instance:
http://example.com:7001/ics/faces/global
This is what the SSL URL for OAuth callback is likely to be:
https://example.com:7002/icsapis/agent/oauth/callback