How to pass process parameters in WEBAPI

How to pass process parameters in WEBAPI which calls process model .


a!startProcess(
processModel: cons!PCI_PM_CALL_INTEGRATIONS,
processParameters: a!fromJson(
http!request.body
),
onSuccess: a!httpResponse(
statusCode: 200,
headers: {
a!httpHeader(name: "Content-Type", value: "application/json")
},
body: a!toJson(
fv!processInfo
)
),
onError: a!httpResponse(
statusCode: 500,
headers: {
a!httpHeader(name: "Content-Type", value: "application/json")
},
body: a!toJson(
{
error: "There was an error starting the process"
}
)
)
)