Navigate to the 'Library' under the 'Community' dropdown menu. From there, type in keywords such as the book's title and the name you published it under. Unless your title is outrageously unique it'll save you time to include both the full title and author of the book into the search field.
The bookshelf is linked to Amazon, which means a) You won't have to worry about adding your book to the bookshelf. If it can be found on Amazon you'll be able to find it here. b) Whatever Amazon shows as the information for 'Title' and 'Author' is the same information you'll want to use in your keyword search.
Once you've located your book via the library search you'll need to click on the hyperlink for the book title so you are taken to the physical page for your book (if you see '=search' up in the address bar you are not on the physical page for the book). At the bottom of your book's permanent home on CC you will find a 'click here' link following the question, "Are you the author of this book?" Clicking this link will position your book in the "Books written by CC members" category on the Bookshelf's main page and link you as the author.