How to get CalDAV URL
1. Go to Calendar.
2. Click Calendar menu on the left tab.
3, Calendar Source tab will appear.
4. At the bottom, there will be CalDAV URL. Copy it. This url will be use while setup on Iphone.
Setup on Iphone
1. Settings
2. Password & Account
3. Add Account
4. Other
5. Under Calendar column, click Add CalDAV Account
6. Fill up below details
Server : fill up full CalDAV url that you get from CALENDAR.
Username : Email account
Password : Email Password
Description : Optional
7. Click Next