my quick and easy solution by adding a search in the file /theme/_common/_header.php
$tpl->og_title = $this->page['title'];
$tpl->og_type = 'artículo';
$tpl->og_url = $this->href('', $this->tag, null, null, null, null, null, true);
preg_match('#\(http(.*?)\)#', $this->page['body'], $match);
$tpl->og_image = "http".$match;
$tpl->og_description = $this->get_description();
I hope that someone will serve you too, as it is more comfortable to put the automatic photo from the article.
Greetings and thanks for the help.