You may not be aware of it, but you did actually do an incredible job. Your first Joomla! website is up and running!
You've seen that building your site is a three-step process. First you customize the layout, then you add content, and then you add further functionality (such as a contact form or a poll) to your site.
You can personalize the looks of the site by editing the template files. If you know just a little CSS, you can edit the template files directly in the Template Manager editor screen.
Before you create content pages you create the containers they belong in. These containers are called sections (the top level) and categories (the second level). Create uncategorized articles if you need some content pages that don't fit any category.
To make any content visible on your site there has to be a menu link pointing to it.
You add items to the home page by changing their Front Page setting. In the Front Page Manager you can change the order in which these items are presented on...