Hi, I will try with printscreens but I am using bootstrap css, so perhaps the look is other on your screen.
You go in frontend to an event (eventview).
On the left image you see the registration part if you are not logged in and the settings are like all can see the attending users. Then the number of booked places is black (has no link)
First of all you need to registrate yourself for this event! (I am not sure)
Then the image looks like on the right and the number of booked places has (is in my case orange) a link to the attendees view. You click on it and see the list with attendings, non-attendings invited, waitinglist and the comments.
with the plus icon on top right you can add users.....
Hope you can find this.
Testing JEM 2.3.0 beta3 local on clean latest Joomla (3.9.11) Protostar php7.3.8 (no mails)