You can scan the barcode on the book, enter the ISBN number, or look the book up in a Google search. I started entering my books today. I think it is going to take awhile to get all of my books cataloged! Lol. Here is a screen shot of what it looks like if you look a book up by the title.
Here is the library home screen. You can look books up all of these different ways. You just enter the book and the app categorizes it for you in all of these ways. You can create create and manage your own collections. One of my favorite aspects of the app is that you can keep track of the books you lend out to others. I am always forgetting what I let people borrow and I do not always get the books back so this is a great tool for me.