You will only see the Calendar icon within the toolbar, if the host configured the session to allow Attendees to schedule a follow up meeting. If the host did not configure this when creating the session, it will not be visible to the Attendee.
In session, click on the Calendar icon in the toolbar
Click the Next Meeting Date field to enter a date. Click the time drop-down menus to indicate a a Next Meeting time. Then enter a note in the Description field (optional). Click Send.
An email will be sent to the designated email address set up by the host who created the session.