Update documentation with OAuth and Data Access details

withings-doc/docs/index.md

@@ -5,7 +5,64 @@ You can install the latest version using Nuget
 
 `Install-Package Withings.NET`
 
-## Details (TODO)
+## Details
 
 #### OAuth Authentication
+Withings.NET handles the OAuth 1.0a authentication flow required by the Withings API.
+
+1.  **Setup Credentials**
+
+    First, configure your Withings API credentials.
+    ```csharp
+    var credentials = new WithingsCredentials();
+    credentials.SetCallbackUrl("YOUR_CALLBACK_URL");
+    credentials.SetConsumerProperties("YOUR_CONSUMER_KEY", "YOUR_CONSUMER_SECRET");
+    ```
+
+2.  **Get Request Token**
+
+    Instantiate the `Authenticator` and obtain a request token. This token is used to generate the user authorization URL.
+    ```csharp
+    var authenticator = new Authenticator(credentials);
+    var requestToken = await authenticator.GetRequestToken();
+    var authorizationUrl = authenticator.UserRequestUrl(requestToken);
+
+    // Redirect the user to authorizationUrl
+    ```
+
+3.  **Exchange for Access Token**
+
+    After the user authorizes your app, they will be redirected to your callback URL with `oauth_verifier` and `userid`. Use the verifier to exchange the request token for an access token.
+    ```csharp
+    // In your callback handler
+    var verifier = Request.QueryString["oauth_verifier"];
+    var accessToken = await authenticator.ExchangeRequestTokenForAccessToken(requestToken, verifier);
+
+    // Store these securely
+    var oauthToken = accessToken.Key;
+    var oauthSecret = accessToken.Secret;
+    var userId = Request.QueryString["userid"];
+    ```
+
 #### Accessing User Data
+Once you have the `oauthToken`, `oauthSecret`, and `userId`, you can access the user's data using the `WithingsClient`.
+
+1.  **Initialize Client**
+    ```csharp
+    var client = new WithingsClient(credentials);
+    ```
+
+2.  **Fetch Data**
+
+    Call the available methods to retrieve data. For example, to get activity measures:
+    ```csharp
+    var activity = await client.GetActivityMeasures(
+        DateTime.Parse("2017-01-01"),
+        DateTime.Parse("2017-03-30"),
+        userId,
+        oauthToken,
+        oauthSecret
+    );
+    ```
+
+    Other available methods include `GetSleepSummary`, `GetWorkouts`, `GetBodyMeasures`, etc. Check the `WithingsClient` class for all available methods and their signatures.