Custom CPT Columns // manage_edit-{post_name}_columns. To add the custom fields to the admin columns

WordPress - Custom CPT Columns

<?php
/*
 * Orders - Custom Columns
 */

add_filter( 'manage_edit-orders_columns', 'my_edit_orders_columns' ) ;

function my_edit_orders_columns( $columns ) {

  $columns = array(
		'cb' => '<input type="checkbox" />',
		'title' => __( 'Order ID' ),
		'email' => __( 'Email Address' ),
		'order_amount' => __( 'Amount' ),
		'trans_id' => __( 'Transaction ID' ),
		'order_status' => __( 'Order status' )
	);

	return $columns;
}

?>