Are you asking about requesting a virtual machine against a blueprint? For example, SubmitVirtualMachineRequest(GroupID, BlueprintID, Username) ??
Do you need it to be from powershell? or command line? or c#?
There are examples of each and usually they're delivered in extensibility training as part of the CDK. They all boil down to doing an HTTP post to the rest entities WorkflowOperation & WorkflowOperationArguments which was in the API guide you linked to. We're implementing some more strongly typed interfaces in the future to make this easier.