How do I add a colleague's calender in Evolution from Exchange?

I know it works, because I have 10 calendars, all marked with ews, that somehow I added when I setup Evolution a gazillion years ago. Now we got 2 new colleagues and I'm at total loss how to add them to my calendar. See the 2 pictures: These blacked out calendars are calendars from my colleagues I can view in Evolution. So somehow I added them. I just don't remember how. We have Windows Exchange Server, everybody but a few of us use Windows 10, so that's not a problem. There's a few of us that use Mac or Linux. Mac too is no problem, just Linux.