How to create custom widget for wordpress admin dashboard ?

Follow the below code

function example_add_dashboard_widgets() {

 wp_add_dashboard_widget(
                 'example_dashboard_widget',         // Widget slug.
                 'Example Dashboard Widget',         // Title.
                 'example_dashboard_widget_function' // Display function.
        ); 
}
add_action( 'wp_dashboard_setup', 'example_add_dashboard_widgets' );

function example_dashboard_widget_function() {
 
 echo "Hello World, I'm a great Dashboard Widget";
}