You've created a full-blown article, consisting of text and an image. Moreover, you've divided the article text into an intro text and the main article text. This way Joomla! will be able to separately display the intro, with a Read more link to the full article. In the editor, the separation is indicated by a red dotted line.

You've seen this division at work on the sample site home page that contains several short intro texts. Only when a visitor clicks on the accompanying Read More link they are taken to a page with the full article text.

To the article you just created, you added an image from Joomla!'s default image set. For testing purposes that's okay, but in real life you'll want to add your own imagery. To do this, click on the Image button at the bottom of the article editor screen. In the pop-up screen, you'll see an Upload box. Click on Browse files to find an image file on your hard drive. Select the image file and click on Start Upload. A thumbnail of the uploaded image will appear among the other thumbnails (you may have to scroll down if there are a lot of pictures). Click on the desired thumbnail. Choose the appropriate Align setting and click on Insert. The pop-up window closes; your picture is inserted.

The article you've just created is ready and it's stored in Joomla!'s database—but it's still invisible on the frontend of the site. That's because there's no link pointing to it. The Main Menu is empty, except for the Home link.