The following instructions explain how to use Outlook to create an ICS file (iCalendar) in Windows:

1. Create the calendar item:
   a) Launch Outlook and select the New Appointment option to start a new calendar item.
   b) Complete the event’s required information, including the title, start and end timings, venue, description, and list of guests.

2. Save the file as an iCalendar file:
   a) Select the File tab.
   b) Click Save As and specify where you want the file to be saved.
   c) Choose iCalendar Format (.ics) from the drop-down selection under Save as type option.
   d) Select Save.