Accepting Calendar Shares - Outlook Web Access

1. Go to the email indicating that someone has shared a calendar with you.  It will look something like this:
   
    
2. Click the Accept button.  The new calendar will then be shown in the list of calendars you already have (in the People's calendars or Other calenders section)
    

Optional steps

If you have several calendars, you probably want to give each one a distinct color.  To change the color for any calendar (ones shared with you, or your default calendars), do the following:

1. Click the three dots to the right of the calendar name.
   
2. Go to Color (to give the calendar a color) or Charm (to give an icon to the calendar) or both.