In order to set a Google Presentation to loop, or automatically advance through the slides, you need to publish it to the web.
To do this:
  1. Open your presentation, click File, and then select "Publish to the Web".
  2. Choose the amount of time before the slides advance.  You can also select the option to have the slideshow begin automatically and to restart the slideshow after the last slide (looping).
  3. Click “Published content & settings”. This will allow you to require viewers to sign in to in order to view the presentation. If you want to restrict viewers to CCPS-only, be sure to check the box.
  4. When you have your settings the way that you want, click “Publish” (or “Start publishing”).  If a confirmation box appears, click “OK”.
  5. After clicking Publish, a new link will appear in the window. You need to use this link instead of clicking “Present”. Clicking “Present” will show the Slides without auto-advance or looping.
  6. You can still edit the content of your presentation after you Publish to the Web.  If you want to change the auto-advance: Go back to Publish to the Web, change the settings and copy the new link.