Add and make new image sizes available in WordPress Uploader for Daily Dish Pro Theme - Reference http://www.wpmayor.com/how-to-add-custom-image-sizes-to-wordpress-uploader/

functions.php

//* Add new image sizes
if ( function_exists( 'add_image_size' ) ) {
add_image_size( 'featured', 720, 405, TRUE );
add_image_size( 'archive', 340, 191, TRUE );
add_image_size( 'sidebar', 100, 100, TRUE );
}

//* Make new image sizes available in WordPress Uploader
add_filter('image_size_names_choose', 'my_image_sizes');
function my_image_sizes($sizes) {
	$addsizes = array(
		'featured' => __('Featured'),
		'archive' => __('Archive'),
		'sidebar' => __('Sidebar')
	);

$newsizes = array_merge($sizes, $addsizes);
	return $newsizes;
}