Where do I find key for custom fields post pictures?

What makes you think you need a custom field? Those sites use 2 completely different themes.

How do I enter different pictures for either of the sites? I am having same problem with both sites.

anyone had this problem?

I have tried everything except the right way. How do you add these little pictures??????

look for the $key value defined in the get_post_meta() function in your theme’s template pages

<?php
    //$custom_field_value = get_post_meta($post_id, $key, $single);
      $custom_field_value = get_post_meta($post_id, 'thumbnail', $single);

?>