Please follow the below steps if you do not see the OpticsPro for Photos extension when in the Apple Photos edit screen.
On your mac, navigate to /Applications, locate DxO OpticsPro for Photos app, and simply run it once.
Within Apple Photos, when selecting 'extensions' select 'more...'
and ensure that the DxO OpticsPro for Photos is enabled.
Once done, you should be able to see the DxO OpticsPro for Photos option in the extensions dropdown.
If you need further help, please open a ticket with our support team HERE.