Reply To: How to change the "Featured Image" size of blog post ?

You can change or add more image sizes to select from by looking in your functions.php file it will look something like this –

// Add new image sizes 
add_image_size( 'featured-img', 730, 420, TRUE );
add_image_size( 'featured-page', 341, 173, TRUE );
add_image_size( 'portfolio-thumbnail', 348, 240, TRUE );

then just copy/paste one of those lines and change the number to the sizes you want.

Also, I don’t think you can center those images by default since the Genesis Framework (not the child theme) adds the images with either an alignleft or alignright class to the featured images.