How to clear the warning 'Replace the default system notification settings with actual data?'
The warning means that the notification settings have not been configured for your cloud and are still their default/dummy values. This is found in Settings -> Configuration under the Email header.
System host - should be domain or URL for the control server
System email - outgoing email address for the control server
System support email - Who gets emailed notifications / warning from the control server (1 email address only)