Reply to a shared calendar invitation
People who are invited to a shared calendar receive an email invitation. Invitees to a private calendar must have an iCloud account and can accept the invitation by signing in to iCloud.com. Invitees can also accept an invitation using Calendar (or iCal with OS X v10.7.5) on a Mac, or the Calendar app on their iPhone, iPad, or iPod touch.
Reply to an invitation
Open the email invitation and click Join Calendar.
iCloud Calendar opens.
The shared private calendars that you join appear in the sidebar of Calendar on iCloud.com and in the Calendar app on your iPhone, iPad, and iPod touch. They also appear in Calendar (or iCal with OS X v10.7.5) on your Mac, and in Microsoft Outlook on a Windows computer.