Confirm with your printing service the book's page dimensions and amount of bleed required. The dimensions for the cover spread will be larger than interior page spreads because it includes the width of the spine as well as the front and back covers.
Create separate documents for the cover spread and for the body of the book. Select "Page Size" in Adobe InDesign's "New Document" dialog box, and enter the final "trim size" for the book page or the cover spread.
Enter the amount of bleed in the "Bleed and Slug" section of the "New Document" dialog box, using the dimension provided to you by the printer, normally around 1/8th of an inch.. It's usually uniform on all sides.
Place photos and images that you want to bleed off the page so they extend to the bleed guide that surrounds the page layout.
Export as a PDF when you've completed the book design, and if your printer accepts PDF files. In the dialog box that appears, use the drop down menu to select the preset provided by the printer. Then select "Marks and Bleeds," and in the new menu, be sure the "Use Document Bleed Setting" is checked. Normally you do not need to check "Printer Marks" as those will be added at the printing service.