Unfortunately, Atticus is not a graphic design program, so it doesn’t include tools for creating book covers. You’ll need to use a design program like Book Brush or Canva to create your cover.
For eBooks, once you have your final .jpg cover design, you can insert it into Atticus so it publishes with the book.
For print books, all manufacturers (such as KDP or IngramSpark) require a separate PDF cover file, which does not get uploaded into Atticus. I’d recommend checking the specific cover requirements of the platform you’re publishing with.
While Atticus doesn’t provide cover design tutorials, you can find helpful guidance on Kindlepreneur.com, including this article on book cover design.