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.

If you have the theme activated, just click on the theme options under the Appearance pane and start at the top. Go through each type of option, try things out. That's the way I learned. If you get stuck on particulars, do a search for the issue here. If you really can't find the answer that way, then post a detailed question in the proper forum.

One useful thing I did is to look at the Showing Off thread to see how many wonderful ways people are using this theme.

I know I'm missing something because this theme is so popular.

But I don't see any page templates to choose from. That seems to me to be a basic. Do I have to create my own?

Also the basic CSS only addresses alignment. Where's the CSS for h1, p, etc?

Maybe I need to find a theme with less flexibility and more specifics built into it?

This theme is popular because YOU get to customize it. In a way it is a blank slate that you can paint the way you want. There are four setting files in the styles folder in the theme you can import, but do as Paulae suggested and take a look at the showing off thread and look at what some users have created and how they have put their own stamp on their sites

I'm impressed...

Can I look at the source on a WP website the way I can on a non-CMS site so I can apply the techniques others use to my own site?

If not, it's just frustrating.

Yes and no - yes you can view the source of almost any web page you visit WP or not
No because Wordpress builds the pages dynamically, there is no source until someone requests the page. This is why wp is popular. You can add a new post and you are done. You don't have to upload a new page since there is no page.

You should visit wordpress.org and do some reading about what wordpress is and how it works so you have some background when you start building your site