I have decided to stop using iCloud Photo to store my photos. Now I want to re-enable using iCloud to hold my iPhone and iPad photos. How do I do it.

I have various Apple devices--- iPhone, iPad, MacBook Air and iMac. I recently decided to move all of my iCloud photos to the iMac hard drive so that could easily process them using Photoshop if I desired. I foolishly decided that I did not want to store iPhone or iPad photos on/in iCloud so I said don't do that. A few hours later I woke up and bought 50GB storage and wanted to undo what I had just done. That is, I now want to re-enable the storing of iPhone and iPad photos on iCloud.

Seems like a simple thing to do, but I can't find a sequence of steps on apple.com that work. I am not an amateur at computing. I have 5 Macs and various other Apple devices. And have been able to solve most problems myself. This one seems trivial, but the info on apple.com does not seem accurate for my iOS or my MacOS devices --- MacOS: Mojave 10.14.16, SE (2n ten) iPhone iOS: 16.51, iPadOS: 16.3.1.

Can you help me? Thanks in advance