Check Storage
You can check on available storage and what apps are using the most storage space in Settings 
> [your name] > iCloud > Manage Storage.
Restoring your device from iCloud backup
You can restore the data on your device from your most recent iCloud backup by doing the following:
- Make sure that you have the most recent version of iOS. You can do this by going to Settings > General > Software Update.
- Go to Settings > [your name] > iCloud > Manage Storage. Here you should see a list of Apple devices that have been backed up using iCloud. Choose a device to see the date and size of the last backup. Make sure the backup is recent as restoring data from iCloud will overwrite any data currently on your phone.
- Go to Settings > General > Reset and tap Erase all contents and settings. Before you do this, make sure that you want to replace this data with your most recent backup.
- The Apps & Data screen should pop up automatically. This screen presents you with options for restoring the data on your now empty device. Tap Restore from iCloud Backup.
- Finally, sign in to iCloud and choose the backup you wish to use.
If you’ve just purchased a new iPhone and your last phone was also an iPhone, the Apps & Data screen will pop up automatically and give you the option to restore the new phone with the last backup from your previous iPhone.