The Featured Image module is in the Post modules category, which appears on when you're editing a Singular-type Themer layout.
The Featured images module displays the featured image that you set on an individual post or page in the WordPress editing screen.
Under the hood
The Featured image module is a "shortcut" module. It's actually a Photo module with a field connection set to Post featured image in the Photo field. When you open this module for editing, you'll have the regular Photo module settings for cropping, alignment, captioning, and linking.
The field connection requires that the Photo source field be set to Media Library because that's where WordPress featured images come from.