Hey Karen,
Great question! I tried playing around with some settings, but there is nothing that will automatically recognize the first weekday of the month in a succinct way when creating recurring events.
The way I was able to do it was using the Date recurrence option and choosing a specific date to recur:

And, once you set that, you can click the Add Another Rule button to create another Date condition and so on and so forth until you have the recurrences you need.
I know that’s a bit more manual than you are probably hoping for — in fact, I think this would be a great idea to add to our feature request forum if you have a chance. Although I haven’t seen this request come up before, I can see how it would be super useful.
Cheers,
Geoff