When you complete the steps for defining the component and component attribute to use as the drag source, the visual editor should look similar to this:
The editor breadcrumb links just above the editor tabs (near the bottom of the editor window) show the path from the currently selected component back to its root parent component. The last component in the path (shown in bold font) is the currently selected component; the component names preceding the selected component comprise the path of parent components. Clicking any component in the path selects that component on the page.
In the XML editor, the code for the image component looks like this: