How do I set a max limit on attendees?

Inside your event, click on the Details tab.  You will see a field called “maximum registrants”.  Type in the maximum number of attendees your event can accommodate.  Ex: If you select 200 as your maximum registrants, the 201st invitee to register will see a notice on the registration page informing them that the event is full, and they will need to contact the event manager if they wish to attend.