We'll need designed and print-ready PDF files (one file for the cover, back/spine/front, and one file for the interior) for printing.
Our file guidelines are here.
This video will walk you through how to set up your interior file for bleeds and also how to export those bleeds when you create a PDF of your interior. It also shows how to export a single-paged PDF file of the interior, instead of spreads.
You don't have to use Adobe InDesign for layout, but our guidelines assume you are. If you can create a PDF from another application, that's fine, just make sure it meets the requirements of the bulleted list on the main support page (scroll down).