The directions are here: WordPress Widget
Currently only one of the three default shelves (read, to-read and currently-reading) can be shown in each widget, but you can add a widget for each shelf. Maybe they will add support for custom shelves later, so we can display our favorites.
10 ways you can help an author this holiday season (spencersiedel.booktrib.com
How can I support authors on goodreads? (debsanswers.wordpress.com)
- Widget Nirvana (nilaewhite.wordpress.com)
- The Custom Google Search Plugin Enhances Your WordPress Search Results (pressography.com)