How to include widgets through a plugin or theme files.

include_widgets.php

add_filter( 'acfw_include_widgets', 'add_include_widgets' );

function add_include_widgets(){

	$acfw_widgets = array(
		array(
			'title' => 'Test Widget 1',
			'description' => 'A widget test from functions.php',
			'slug' => 'test-widget',
			'id' => 'Test_Widget',
		),
		array(
			'title' => 'Test Widget 2',
			'description' => 'A second widget test from functions.php',
			'slug' => 'test-widget-2',
			'id' => 'Test_Widget2',
		),
	);
	
	return $acfw_widgets;
	
}