The Wikimedia Commons has millions of images. To insert one of these image into a Wikipedia article, first click the section of page where you want the image to be placed.
The dialog box displays an initial set of suggested images from the Commons, based on the title of the page you're editing. You can change the search by typing in the dialog's search box.
Once you see the name a file you want, click on its thumbnail image. This places the image onto the page you are editing. You can then drag the image to change where it's placed on the page.
