Backing up your iPad using iCloud is easy. You basically set it up and forget it. It takes care of backup while you are not using iPad. This is how you activate iCloud backup in iOS:
Go to Settings > tap your name at the top > iCloud > iCloud Backup.
Activate iCloud Backup.
The device has to be connected to WiFi, a charger and have screen lock activated for automatic sync to start.
You can also start a backup manually at any time by tapping Back Up Now when you are in iCloud Backup settings. It is a good idea to back up iPad before you update iOS or have your device serviced.
If you want to see your available backups, go to Settings > Storage & iCloud Usage > Manage Storage (under iCloud). Below the heading Backups there is a list with all your backups. Tap on any of them to see when they were created or to delete them.
To re-install a backup to your iPad, you have to do a restore.