Ignore the previous advice. The book templates in Pages are for eBooks.
1. You should have 16pp, printed books/booklets come in sets of 4pp.
2. How are you going to print this? Digitally, desktop, commercial offset? How are you going to bind the pages.
3. If you are having it printed commercially talk to your printer what format they want your file in (probably not .pages). They probably can do the imposition for you.
4. If you are printing this yourself on your own printer you will need to print to PDF at best quality, then take the .pdf file and pass it through Imposition software which will do the page placement for you. Look for the software in the Apple Store or Mac update.com
5. Failing that you can manually reorder the pages of the PDF into the correct imposition order which you get by making up a dummy booklet with blank numbered pages and unfolding it to see what goes where. Which all depends how large a sheet you can print on and how you will bind it. To print longer runs you can drag the individual pages from the .pdf from Preview and bring them into a second Pages document where you position and orient them in the Imposed order.