Hi dave69,
It needs code customization. You may add the image in the editor of the page. Using featured image will work on business template as you can see in services and recent work. That image is displayed from the featured image. If you like to display in other page too then customize the code. The below code is used to display the featured image. https://codex.wordpress.org/Function_Reference/has_post_thumbnail
if ( has_post_thumbnail() ) {
the_post_thumbnail();
}
else {
echo '<img src="' . get_bloginfo( 'stylesheet_directory' ) . '/images/thumbnail-default.jpg" />';
}
Got to theme folder -> inc -> structure -> content-extension.php on line no 201 to 260. You need to add the above code. Then your featured image will be displayed.
While customizing the code first of all create a child theme then only customize the code to be safe from data loss. If you make direct changes in the code then you need to make the same customization again and again while updating to new version.
Thank you!