Preferred Styles are preset, custom box configurations. There are preset box styles that come with the application, and the user may configure custom Preferred Styles.
Under the Design tab select Styles.
Choose Add to if you have configured and selected a box style you wish to add to the library or select Preferred Styles if you want to apply a style from the list to a selected box.
Preferred Styles: Example
Notice that the styles can be applied with any scope, or they may be applied to individual employees meeting specific rule criteria.