If you click on the three dots beside the title Body in the left navigation panel, you'll be able to choose Begin On > Right-side and that will apply to all the chapters in the body content of your book.
You can also find this setting by clicking on the three dots beside the titles of individual chapters and pages, if you want to be more specific.
After you have adjusted these settings Atticus will automatically add blank pages as needed to ensure that pages start on the correct side of the spread.