One of the concepts of Balder is a base class called Game. For doing cross platform development, the Game class will be your entry point into Balder, it will serve the content to the engine and gives you a place to add game logic.
Some platforms, such as Silverlight, is supported to be able to not use a game class, but then one loses multi-platform support.
All you need to do is to inherit from the Game class found in the Core component.
public class MyGame : Game
In order for the Game to recognized as an entry-point, Balders' runtime needs to be aware of it. This is something that differs between the platforms, please go to the specific platform section for details on this.