Once a Post has been created, or subsequent to it, any media can be added. The media can be inserted virtually anywhere into the body of the post, or it can be added as a “Featured Image”. A “Featured Image” is one which will display above the Post once the post is published and viewed.
The button titled “Add Media”, shown above and displayed in the attached graphic, will take you to the Add Media screen. From there you can ‘Upload’ a new file to the library or choose a photo from those in the library.
The “Add Media” screen will look like this, very similar to the “Media Library – Add New” page. You will see the same ability to ‘Upload Files” or select from the ‘Media Library’. Also available from this screen are the options to “Create Gallery”, various Audio and Video features, and the selection of a “Featured Image”.