How do I consume web API from console application (only post method) and save the data to my database?

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I am getting 200 ok from the "postresponse" object. Can anyone please guide me how to i catch the data and save it to my database?
I am getting a response from the postman. But when I run my console application i cant catch the response data. Please someone guide how to do this? This is GPS data, providing API from one of our client, and i just want to consume the data and save the response from the API. I am passing vechile Numbers,start and end dates and getting the data in fields.

static async Task RunAsync()
        {
            using (var client = new HttpClient())
            {        
                client.BaseAddress = new Uri("http://api.blabla.com/");
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                try
                {
                    // HTTP POST
                    var dat = new APIEntity()
                    {
                        unitCodes = new List<int>() {19215,19216,...}, // Multiple vehicle numbers
                        start = DateTime.ParseExact("2018-03-12 01:00:00", "yyyy-MM-dd HH:mm:ss", null), // format : ISO 8601.
                        end = DateTime.ParseExact("2018-03-12 23:00:00", "yyyy-MM-dd HH:mm:ss", null), // format : ISO 8601.
                        fields = new List<string>() { "unitCode", "timedate", "latitude", "longitude", "ignition", "velocity", "positionerror", "digitherm5", "direction", "distance" } // I should get the values of the fields and save it to my database.
                    };

                    HttpResponseMessage postresponse = await client.PostAsJsonAsync("api/points", dat);
                    postresponse.EnsureSuccessStatusCode(); // postrespones code 200 ok.
                 if (postresponse.IsSuccessStatusCode)
                    {
                       ???????? // how to fetch the data?
                     }
                }
                catch (HttpRequestException e)
                {
                    Console.WriteLine(e.Message);

                }
            }
        }

     static void Main()
        {

            RunAsync().Wait();
        }
My Model is:
public class APIEntity
    {
        public List<int> unitCodes { get; set; }
        public DateTime start { get; set; }
        public DateTime end { get; set; }
        public List<string> fields { get; set; }
    }

For your reference : Postman Request is :
{
"unitCodes": [
  19215,
  19216,
  19224
],
"start":"2018-03-20T09:00:00.000Z",
"end":"2018-03-20T15:10:00.000Z",
"fields": [
  "unitCode",
  "timedate",
  "latitude",
  "longitude",
  "ignition",
  "velocity",
  "positionerror",
  "digitherm5",
  "direction",
  "distance"
]
}


and Respose is :
{
    "status": "Success",
    "data": [
        {
            "unitCode": 19215,
            "timedate": "2018-03-20 09:01:23",
            "latitude": 25.216296552475924,
            "longitude": 55.26109752059169,
            "ignition": false,
            "velocity": 0,
            "positionError": false,
            "seatCount": 0
        },
        {
            "unitCode": 19215,
            "timedate": "2018-03-20 09:11:23",
            "latitude": 25.216199149650755,
            "longitude": 55.261200652994816,
            "ignition": false,
            "velocity": 0.03,
            "positionError": false,
            "seatCount": 0
        },
        ......
...............
}