get custom fields value in wordpress theme

To be used only inside WordPress’s Loop
 
<?php echo get_post_meta($post->ID, 'custom_field_name', true); ?>
 
It displays the value of the custom field. Replace “custom_field_name” with the chosen name of your custom field.
 
To display the value outside the loop use
 
<?php
global $wp_query;
$postid = $wp_query->post->ID;
echo get_post_meta($postid, 'custom_field_name', true);
?>