When an item says it is On Shelf, that means it is available and in the stacks. To locate the item you will want to use the call number that is listed within the item record. Make note of the call number and then go to the floor of the library on which your book is shelved. (Go here to view maps of all floor locations and corresponding subject for call numbers.) If you cannot find the book, you can check the book sorting room where most of the time you will find a staff person who will give additional assistance.