step-by-step instructions for customizing Atahualpa?

I chose Atahualpa for my very first WP website. I know HTML and CSS (have done websites from scratch) but I'm having a hard time finding guidelines on where to start and how to proceed. I've already installed WP and uploaded Atahualpa so I'm beyond that.

I've found many HOWTOs on specific topics, but I'm looking for a more general overview. To start, where can I see the different layouts possible with Atahualpa so I can choose one (and how do I choose one)? What's the next step, etc? Is there a basic instruction sheet for this theme or should I be looking elsewhere?

Thank you. Your help is appreciated.