Open Finder; click iCloud Drive in the Finder sidebar (or in the Finder Go menu);
Open a 2nd Finder window (Finder File menu > New Finder window).
In the new Finder window navigate to the Pictures folder in your home folder (this is the default folder for photos but you can use something else)
Drag your Photos Library from the iCloud Drive folder to the Pictures folder.
When you next try to open the Photos app you will need to direct it to the new location. If you hold down the option key while opening the Photos app it will ask you for the new location.
If you want your photos to sync with iCloud, rather than using iCloud Drive turn on iCloud Photos. See: Set up and use iCloud Photos - Apple Support
If you want to potentially reduce the storage used for photos on your Mac, turn on Optimize Mac Storage (open the Photos app, click Settings in the Photos menu, click iCloud at the top of the Settings window, put a check mark in front of Optimize Mac Storage.