I am not quite sure that I understand your questions correctly. Can you please try to shed some light on your exact problems? Generally Microsoft Expression Blend is a user interface design tool, which you can use to create rich and interactive web and desktop applications for Silverlight/WPF. Furthermore RadControls for Silverlight provide full Microsoft Expression Blend support. In our online documentation for these controls you may find more info on that matter, please check this link. RadControls for Silverlight are tightly coupled to Sitefinity and can be directly incorporated in your pages in the form of custom user controls based on particular business logic. I believe that the following Sitefinity related articles might be also of help on that matter: "Create a Book widget", "Create a CoverFlow control" ,"Create a “Hello, world!” widget".
the Telerik team