Right click on any image you find on the web (or even that you've Googled) and select "Copy Image Address" from the menu that appears. Once you're on Terb go to the Insert Image icon as previously stated and paste the URL and click OK. Bear in mind that some web-sites might disable the ability to right click an image.
You can do the same with links to web-pages and YouTube videos, but you can only link one video at a time.