Select "New" in the upper right hand corner to add a new author. A name is required before the author can be saved to your database. Once you have entered a name, you can press "Search Author" to look up books by the author via the book search. You can also select "Add Book" (only displayed in Edit mode) to add a book manually.
Authors can be sorted by name, rating, role (illustrator, editor, etc.), or the custom fields.