RETURNING BORROWED eBOOK TO LIBRARY

I recently purchased an Acer Iconia One 7 and downloaded Adobe Digital Additions. I successfully borrowed and read an ebook through my local library download service. I would like to return this book but have been unable to pull up any tab that gives me this option. Nor have I been able to get a page called "Bookshelf" from which, in theory, I should be able to return the book.