Have you created your custom field correctly?

 Have you created your custom field correctly?

Make sure to read the readme file that came in your theme's ZIP file and follow the thumbnail custom field creation instructions. In most cases you will need to create a custom field with a Name/Key of "Thumbnail" (this is case sensitive) and a Value of your image URL. Some themes also require multiple custom fields to be created, usually for Featured Articles. In this case you would need to create a second custom field, as outlined in the readme, for all featured articles.