1) Go to Settings on your iPhone/iPad
2) Tap Password & Account
3) Tap Add Account
4) Other Press
5) Tap Add CalDAV Account
6) Enter the following details for your account:
Server: To get the server URL, you can do the steps below:
Login to cPanel -> Email Account -> Select in Email Account -> Configure Calendar and Contacts -> Direct URL for Calendar and Contacts
May get URLs from Secure SSL/TLS URLs or Non-SSL/TLS URLs in Calendar
Username: Full email address
Password: Email account password
7) Tap Next on the top right corner to verify the account.
8) Tap Save in the top right corner.