Open the "Calendar" cube.
Click on the "Calendars" button.
Choose the calendar to which you want to add users and click on the calendar name.
Select "Add members".
This will enable you to select different users.
Note: You can only add users from your contacts list.
Click "Ready" to close the 'add' screen.
The name of all added participants will now be displayed at the bottom of the screen.
Click on "Ready" to save the changes made to the calendar.