To add a book to your Favorites, simply tap on the heart icon on the top right corner once you’re in a book. It will automatically be saved to your Favorites.
To add an activity as a Favorite, while you're still in the Library, press and hold your finger down on the activity until you menu pops open. Select the Favorite option.
You can view your Favorites directly on the bottom Navigation bar.
To remove a book from your Favorites, tap on the book to open it and then tap on the heart icon again.