To capture experience data using the Sitecore ASP.NET Rendering SDK, you can follow these steps:

1. Set up Experience Analytics: Before capturing experience data, ensure that Experience Analytics is properly configured in your Sitecore instance. This involves setting up the necessary reporting database and configuring the analytics-related settings.

2. Initialize the Tracker: The Sitecore Tracker is responsible for capturing and storing the experience data. Initialize it in your code by calling the `Tracker.StartTracking()` method. This will start tracking the user's interactions on your website.

3. Track Events: Use the Tracker to capture various user events that you want to track. Events can include page visits, button clicks, form submissions, and more. You can track events by calling the `Tracker.Current.CurrentPage.Register()` method and providing relevant event data.

Here's an example of how to track a page visit event:

```csharp

var pageEventData = new PageEventData("Page Visited", Sitecore.Analytics.Model.Constants.PageEventItemId)

{

    ItemId = Sitecore.Context.Item.ID.ToGuid(),

    Data = Sitecore.Context.Item.Paths.FullPath

};

Tracker.Current.CurrentPage.Register(pageEventData);

```

4. Track Goals: Goals represent specific actions or conversions that you want to track on your website. Use the Tracker to track goals by calling the `Tracker.Current.Interaction.RegisterGoal()` method and providing the goal ID.

Here's an example of how to track a goal:

```csharp

var goalId = new Guid("YOUR_GOAL_ID");

Tracker.Current.Interaction.RegisterGoal(goalId);

```

5. Track Custom Data: You can also capture custom data about the user or their interactions. Use the `Tracker.Current.Session.CustomData` property to store custom data as key-value pairs.

Here's an example of how to store custom data:

```csharp

Tracker.Current.Session.CustomData["CustomKey"] = "CustomValue";

```

6. End the Interaction: Once you have captured all the necessary data for an interaction, end the interaction by calling `Tracker.Current.EndTracking()`.

7. Process and Analyze Data: After capturing the experience data, Sitecore will process and store it in the Experience Analytics database. You can then use the Experience Analytics tools within Sitecore to analyze and visualize the captured data.

Note: Make sure you have the necessary Sitecore assemblies referenced in your project and that you have appropriate permissions to access and modify the Sitecore instance.

These steps should help you get started with capturing experience data using the Sitecore ASP.NET Rendering SDK. For more detailed information and advanced usage, refer to the Sitecore documentation and SDK references.