Sign in to iCloud.com with your Apple ID: https://www.icloud.com/photos
Open the Photos app on your iPhone or iPad
Open the Photos app on your Mac
Enable iCloud Photos on iPhone/iPad: Settings → [your name] → iCloud → Photos → Sync this iPhone
Enable iCloud Photos on Mac: System Settings → Apple ID → iCloud → Photos → Sync this Mac
Enable iCloud Photos on Windows: Install iCloud for Windows → open iCloud for Windows → Photos → check iCloud Photos → Apply
Access iCloud Photos on Windows via the iCloud Photos folder in File Explorer
View shared albums: iCloud.com → Photos → Shared → open the album
View recently deleted photos: iCloud.com → Photos → Recently Deleted
Use the search bar in Photos (iOS/Mac/iCloud.com) to find photos by people, places, or dates