Using the Dialog Editor to Add Controls
When you create your dialog-template resource with the dialog editor, you drag controls from a controls palette and drop them into the dialog box. This adds the specifications for that control type to the dialog-template resource. When you construct a dialog object and call its Create or DoModal member function, the framework creates a Windows control and places it in the dialog window on screen.
You can instead create controls by hand if you want. This is more work.