Problem with applying a custom object to ASP.NET web application

Hi everyone!I am using the Visual Web Developer express and I am trying to create a simple web application,but also I need to apply a custom class written in C#.How am I supposed to procceed after I have created the class so I can use it and view it on the web page?I mean when I creat objects of that class and I work with them?
Example: I have a class Dog with all its fields and methods and I instatiate an object then I call its methods etc... where do I write this code and how do I visualize the result on the web page?

Thank you!