Add external drive Photo Library to iCloud
I am currently using icloud to backup and store my photo library. I also have an external drive filled with older photos (these photos are not on my current computer so they are not currently syncing with icloud). I took them off my computer and loaded them onto the hard drive in an effort to save space on my computer. These old photos are in a separate iphoto library on the external drive. I would like to add these photos to the cloud so that they are backed up and accessible. Can anyone tell me what I need to do to make this happen?
MacBook Air (13-inch, Early 2015), iOS 10.3.3