How can I add a calendar event in my iCloud calendar using a downloaded ics file

I have a downloaded ics file; that I want to add to my iCloud calendar using a browser on Windows 11.

Some help topics indicate that I'd need to add to Outlook (or another calendar), and then sync with the iCloud calendar. Which seems very messy

Other options are (i) email the ics to myself, and use my iPhone to open the email, click the attachment. and it should add to my iphone Calendar app (ii) import the ics using my iCloud/calendar on my desktop

Both the above don't work!

Any suggestions please. Thanks