Make sure you've created a WebCal link:
You can add your webcal link to Outlook by following these steps:
The go-to your Mac and add this link as a subscribed calendar.
- Open the Calendar app
- In the calendar app select
menu File > New Calendar Subscription and put the URL in there.
Set the location field to iCloud to sync across all your devices (you need to be logged in with the same apple id across all devices).
If you have any additionals questions or remarks, please contact firstname.lastname@example.org