"Wow, I've done all this and I still don't have any content on my site!" Well, let's fix that.
First, let me explain that the page your visitor sees first upon entering your site is usually called the "home" page. Drupal calls this the "front" page, much like a newspaper. This page is special to Drupal. I know you're in a hurry, but read about both "pages" and "stories" before you decide which to use to create your front (home) page.
Drupal says, "If you want to add a static page, like a contact page or an about page, use a page." If you're used to building web sites with HTML, this is what you've done in the past. In general a "page" is going to stand on its own and will probably have a menu entry. You may also later add it into a book. When I created my first two sites (based on former static HTML sites, I made the front page a "page;" I have since changed to a "story."
Drupal says, "Stories are articles in their simplest form: they have a title, a teaser and a body, but can be extended by other modules. The teaser is part of the body too. Stories may be used as a personal blog or for news articles." Why they say to use it for a blog, I have no idea; they supply a blogging module as part of the core support.
I have now switched my sites to use stories on the front page. The "welcome" message is one story. I have an announcement story node that any of my admins can edit. If you want to have weather or cartoons, a story is a good idea. Another use is if you are on a net ring - put the ring links into a story.
Drupal says, "A book is a collaborative writing effort: users can collaborate writing the pages of the book, positioning the pages in the right order, and reviewing or modifying pages previously written. So when you have some information to share or when you read a page of the book and you didn't like it, or if you think a certain page could have been written better, you can do something about it."
Another way to use a book is to collect related information together. A book has its own navigation, so it can also be used to de-clutter your menu.
You probably already know what a blog is, but just in case: A blog is a diary, collection of thoughts, or other time-ordered content.
So have you decided what kind of content you want? No, okay, just start with a page; it's easy. As you go create your content, be thinking about the menu as well.