Ok, by the looks of it what you're trying to do is use a custom page link, rather than link to the post URL.
There are a couple of changes you need to make for this to work:
1.) Open up /framework/classes/kclass_display_box.php and find this code:
echo '<a href="'.get_permalink().'" class="more-link">Read more</a>';
Replace it with this code:
$new_link = get_post_meta($post->ID, "new_link", true);
if($new_link) {
echo '<a href="'.$new_link.'" class="more-link">Read more</a>';
} else {
echo '<a href="'.get_permalink().'" class="more-link">Read more</a>';
}
This will dynamically select the $new_link if it exists otherwise default to the permalink.
2.) You need to go to WP admin and edit your post "Consigue el maximo en tu deporte" and create a custom field called "new_link". Enter the URL here that you want to point the Read More to, in your case http://www.alimmenta.com/dietista-deportivo/
This is something that has come up already and I will talk with Kriesi about including this in the next framework update.