Private DNS 1dot1dot1dot1.cloudflare-dns.com can be configured by following these steps:
Open the settings on your phone, then select the 'Connections' menu.
Next, select 'More connection settings'
Select 'Private DNS'
Enable the 'Private DNS provider hostname' option
Enter the following: 1dot1dot1dot1.cloudflare-dns.com, then tap 'Save'
If the connection is successful, the screen will look like the image below