Set the post image to features image

Hi, is there a way to choose a post image (if there are several or evenif there is only one) and set it as the Featured Image without it being addd to the top of the post? For example, we have another WP blog (Genesis Framework) and on a particular post, there are 3 images. One of them is selected as the Featured Image. It does not show at the top of the post, and it can be included in the post or not included at all, however, when the post is shared, it is the image used. Does that make sense?

If you want to specify an image to be a image used in the Facebook like it/send buttons and in the Pinterest, then please use the OpenGraph metabox in the article editor - there you can select an image used for the shared content.