1) First, download the latest version of the HTTP-REST plugin for VCO, which I believe is version 1.0.2 found here:
https://my.vmware.com/web/vmware/details?downloadGroup=VCO_REST_PLUGIN_102&productId=284
2) Once installed, look under Library-->HTTP-REST-->Configuration and run the "Add a REST Host" workflow found there. Beware that I have found it only likes official-looking domain names when using DNS for the VCNS host URL, so "https://myvcns.sitea.local" will probably give you an error, while "https://myvcns.sitea.local.yourdomain.com" will probably work. I used a hosts file entry for my dev box to get around this limitation, but once it is registered it should be fine. You can also try a hard-coded IP address as a test if you are having trouble with this part. I used Basic authentication and Shared Session for the host authentication piece.
3) Next, run the "Add a REST Operation" workflow found in the same location. Choose your new host, give the operation a name, and enter "/api/versions" for the template URL (no quotes).
Set the method to GET.
4) Now run the "Invoke a REST operation" workflow and execute your new operation from the inventory. If all is setup properly, you should see the Status code 200 returned along with the XML content as a string.
5) You can also add an operation that takes variables in the url like this: "/api/2.0/vdn/virtualwires/{vw-moref}", where you will be prompted for the values when invoking this operation.
The way I am actually making calls to VCNS from my workflows right now is to make a call to the "Invoke a REST host" workflow from my outer workflow, where i just simply build up the operationUrl as a string in my code first and set a different string var to "GET" for the request type. This workflow returns a Properties var from which you can extract the status code and the XML content as a string and start parsing out the data you need from there. Hope this helps get you started.
