I cannot find enabled apps

I apologize for the ridiculous question. I am somehow stumped. My instance of NextCloud is self hosted. I have a bunch of apps enabled and a lot of them show up across the top of the page on the dashboard screen. However, there are also a whole bunch of them that don’t appear anywhere. Just picking one ‘Holiday Calendars’ I cannot find anywhere where I am able to enter settings for it. Sorry, I am embarassed by the question. I am missing something super simple.

I think it is part of calendar.

Can you install e.g. https://apps.nextcloud.com/apps/forms or https://apps.nextcloud.com/apps/polls . Both you get a button on the top.