Tell Photos where to Look for Photos

My friend has a Mac running El Capitan. She had been using a portable drive as a "backup". Seems her Photos app was storing the files on the portable drive. In other words, the Photo directory was on the portable drive. I guess that's something she did inadvertently when she set up the drive. Today, she purchased 50G on iCloud. I copied the contents of the portable drive to iCloud. She wants to start working from the iCloud instead of her portable drive or the local drive. My question is, how do I tell Photos that the pictures are now in iCloud? Do I have to import them all over again or is there a way I can change the directory Photos uses and be done with it?

Thanks in advance for your help.