There are a couple of reasons why a record in the catalog doesn't show a call number.
First, if the title is an ebook, it wouldn't have a call number because it's accessed online. To view the book, click on the "Wentworth" link, and then follow the log-in information.
If the book you're looking for is a novel/fiction, it doesn't have a call number because those books are shelved in alphabetical order based on the author's last name. These books can be found on the first floor of the library, on the shelves labelled "Fiction".