SYNCING YOUR iPHONE/iPAD/iPOD TOUCH WITH GOOGLE CALENDAR
Sync your Google Calendar with your Apple device (including iPhone, iPad, and iPod touch) and always have your schedule at your fingertips.
Note: You can also use Google Sync to sync your Calendar and Contacts. It is possible to run CalDAV sync and Google Sync simultaneously.
Syncing via CalDAV is only available for Apple devices running software version 3.0 or above. Learn more about checking the software version on your device.
You need to go HERE (Calendars page) on your computer.
Scroll down the page, to the bottom of the Google Calendar.