Open the app then go to library. Here you can select your book in the list under "All titles" or simply search for it and add it to your list by clicking on the "+" symbol. All the books you have selected as favourites will then appear under "My list".
To help you find your book quickly, you can sort the titles chronologically by date (of upload) or alphabetically.
As soon as you click on the title of the book, the book is selected. The scan view is opened and you can begin scanning.