This article explains how to enable iCloud Photos, My Photo Stream, and Shared Albums on iPads running iOS 12 or iOS 11.
Turn ON Upload to My Photo Stream on iPhone
Follow these instructions to enable iCloud Photos or My Photo Stream on your iPad. You can also turn on Shared Albums and invite a group of people to view your individual photos and videos.
From the iPad home screen, tap Settings.
Scroll down the menu on the left side of the screen and select Photos. In the screen that opens, you have options to enable iCloud Photos, My Photo Stream, and Shared Albums.