If you’re on the mobile app just go to guests / select the event e.g wedding / then on the right you’ll see a drop down that says “all” / change to attending etc
On the computer, it’s a similar process. Guests / select event / select the tab that says “attendance” (it should say groups, menu, seating chart, attendance, lists), under attendance will show you who confirmed etc Here’s the mobile example:
I changed my group names to pending, accepted and declined. Previously they were brides family, grooms family, wedding party, friends etc. once I receive their rsvp, then I move them now from pending to either accepted or declined.