The OCS HTTP API is very well documented in the OCS deployment guide, I would suggest looking there for information on how to set it up and utilize it.
Also, one of the SCXML samples that is bundled with OCS I believe demonstrates how to perform an HTTP Post from SCXML.
It has been a while since I have looked at the OCS API, but you may be able to refer to the SCXML samples to learn how to HTTP Post from SCXML to the OCS HTTP API.