Using External Hard Drive and the Organizer; having problems

I recently started using PS Elements 14 on a Mac desktop.  I originally uploaded all of my images from iphoto to the organizer  but my whole system was running slowly.  I tried to transfer these photos to a new external hard drive that I purchased just for photos but I was not able to restore the link to the photos that were now on the external hard drive. I copied the photos and put them back in iPhoto but moved them to external drive (I found how to do this on line).

I would rather use Organizer but I need the photos to be maintained on the external hard drive to free up my Mac for operations.  Does anyone know how I can do this?