To get started, click the "Website" tab in the left-hand editing pane:
Then, click the "Content" tab in the left panel.
Then, in the menu that appears, select "Files & media":
Next, mouse over the item you'd like to download and click "Edit" on the right hand side:
Hover over the image in the new window that appears:
Finally, right click on the image and select "Save Image As..." to save the image to your computer!