how to add / sync google calendar?

I have a **Xaomi Redmi Note 4G** and have installed PAC-ROM-asrupesh-UNOFFICIAL-PORT.zip from [XDA - \[ROM\]\[PORT\] PAC ROM UNOFFICIAL for Redmi Note 4G Single Sim][1] . I followed the steps from the forum to install the ROM. Now I do not have my Gmail Calendar. If I go to Calendar -> Settings I can see my Gmail account but no other calendar. If I hit **Add Account** there is no Gmail account. If I go to Settings -> Accounts -> Google Account and click my Gmail account I want the calendar to be in my mobile, but I cannot see an option to sync calendar. It is not there. Any idea how to add the Gmail Calender to my current ROM?