If you want to share your FreeBusy availability back into Outlook or Google Calendars so that your colleagues and friends can see the times when you are free/busy internally, here is how to go about it:
Visit https://freebusy.io/icalendar. You would be able to get your URL so that you can automatically share calendar feed
Next, you copy the link and go on either your outlook and google calendar.
Next, you add a calendar and subscribe from the web.
It gets automatically imported and your colleagues are made aware of times you are free or busy.
That's it!
Kindly note that this is available for Professional plans. See: Pricing | FreeBusy