How to upload a document in a SharePoint list using Graph API

We have been trying to add a document to a list item using Graph API but are being thrown a 400 error 🙁 We have the access token and can query the list in question without any problem. Below is the code we are using to try to add the document to the list

string addItemJsonString = "{\"fields\":{\"Title\":\"Dec Word file\"}}";  string requestUrl = " Library/items";  HttpClient client = new HttpClient();  HttpRequestMessage message = new HttpRequestMessage(HttpMethod.Post, requestUrl); message.Headers.Authorization = new AuthenticationHeaderValue("Bearer", accessToken); message.Content = new StringContent(addItemJsonString, Encoding.UTF8, "application/json"); //set the body for the request   client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "application/json; charset=utf-8");  HttpResponseMessage response = await client.SendAsync(message);  if (response.IsSuccessStatusCode) {   responseString = await response.Content.ReadAsStringAsync(); } else   responseString = "Error in response"; 

Any idea of where we are losing it?