After you've run a search, use the left-hand Search Filters, and click on the arrow next to Titles by Discipline to expand that section and select Nursing.
To cite e-books from STAT!Ref, once you've clicked into a result, at the top of the result screen you'll see Download Citations. Click on Download Citations, then copy and paste the displayed citation into a Word document. Then, refer to a citation style guide to format the citation correctly, as an e-book from STAT!Ref.