Here are a few simple tutorials and guides to show how you can work with your windows.
Create a window
Use screen_create_window_type() to create an application window.
Create a child window
Use screen_create_window_type() to create a child window. A window of type SCREEN_CHILD_WINDOW must be associated with a parent so that it can be visible on a display.
Zooming with windows
Several window properties control how Screen displays your window buffer(s) (source image).