How to set Httpwebrequest Authentication header with Authenticationresult

I need to set the auth header for my http web request using the AuthenticationResult I get from AuthenticationContext:

 AuthenticationContext authContext = new AuthenticationContext("http://blabla/token");

 Task<AuthenticationResult> resultTask = authContext.AcquireTokenAsync(
               "http://blabla/service",
               "SomeGuid",
               new Uri("http://authlogin"),
               new Microsoft.IdentityModel.Clients.ActiveDirectory.PlatformParameters(PromptBehavior.Auto, false));

 resultTask.Wait();
 AuthenticationResult result = resultTask.Result;
 HttpWebRequest request = WebRequest.CreateHttp("http://MyApi/method");
 //Set headers for request

I need to pass the authentication result to the header of my request. I know I can do

request.Headers[HttpRequestHeader.Authorization] = //something

I just don't know what that something should be. Any help is appreciated. Thanks