Out of the box, Genesis does not display the Featured Image on posts and pages automatically. To add this functionality you will need to edit your functions.php file to add one or both of the following snippets.
Remember: Editing your live site via the code editor is discouraged. Test out any changes on a local copy of your site first (see this tutorial if you don’t know how) before uploading the updated files to your live site.
Explaining how this snippet adds a Featured Image
The first part of the code above tells WordPress to add (or “hook”) the Featured Image into the page above the page/post title and content. You can change the location of where the Featured Image displays by changing the hook used, say for example from ‘genesis_before_entry’ to ‘genesis_entry_content’ which will move it below the header but above the rest of the page content. To see a visual guide of where each hook is placed on a page this visual hook guide is a great resource.
The second part of the code is the function that the first part is telling WordPress to execute at the hook you specify. In plain English, it says “if the page we are on is a single page or post (and not an archive or something of the like) then display the featured image in the size specified and with the following attributes.” Instead of typing $size you would type ‘thumbnail’, ‘medium’, ‘large’, ‘full’ or a custom image size.
If you leave either $size or $attr blank [ex. the_post_thumbnail(); ] the theme will pull the default set by your child theme, Genesis, or WordPress (in that order). If you would like you can use $attr to specify any attributes you would like applied to all Featured Images called by this function (for example as shown in the code notes above, apply the class ‘alignleft’ to every image)