Custom Fields in Custom Post Type

I am developing a comics website for which I require a custom post type which I created using below function in functions.php. Now I am looking for few custom fields to upload multiple images as snapshots of comics. Could someone please help me?

function my_post_comics() {
	$labels = array(
		'name'               => _x( 'Comics', 'post type general name' ),
		'singular_name'      => _x( 'Comic', 'post type singular name' ),
		'add_new'            => _x( 'Add New', 'comic' ),
		'add_new_item'       => __( 'Add New Comic' ),
		'edit_item'          => __( 'Edit Comic' ),
		'new_item'           => __( 'New Comic' ),
		'all_items'          => __( 'All Comics' ),
		'view_item'          => __( 'View Comic' ),
		'search_items'       => __( 'Search Comics' ),
		'not_found'          => __( 'No comics found' ),
		'not_found_in_trash' => __( 'No comics found in the Trash' ),
		'parent_item_colon'  => '',
		'menu_name'          => 'Comics'
	);
	$args = array(
		'labels'        => $labels,
		'description'   => 'Holds comics and comic specific data',
		'public'        => true,
		'menu_position' => 5,
		'supports'      => array( 'title', 'editor', 'thumbnail', 'excerpt', 'comments' ),
		'has_archive'   => true,
		'rewrite' => array("slug" => "comics"),
		'capability_type' => 'post'
	);
	register_post_type( 'comic', $args );
}
add_action( 'init', 'my_post_comics' );