Authorization before post request c#

i have a problem with authorization on a web server. I want to make a post request, but i am not authorized.

Here is the example of my post request:

using (var client = new HttpClient())
        {
            client.BaseAddress = new Uri("https:/test.test/");

            var content1 = new FormUrlEncodedContent(new[]
            {
                new KeyValuePair<string, string>("object", "10"),
                new KeyValuePair<string, string>("type", "1"),
                });
            var result1 = client.PostAsync("/api.php?action=someaction", content1).Result;
            string resultContent = result1.Content.ReadAsStringAsync().Result;
            Console.WriteLine(resultContent);
        }

How can i authorize before sending this post request?