How can I create events in another user's default calendar?

New to APIs, have recently been experimenting with the Graph Explorer, as I need to add dozens of events to users' default (not shared) calendars.

It appears that I can only work as a delegated user. All of the documentation I've read says that in order to read/write, I need app-level permissions. I understand how the access differs, but what, exactly, does "app" mean? Do I need to create an actual application to call the API without involving the user?

I'm not a developer or sysadmin, though I know some VBA and have worked in Power Automate, so I'm not completely tech illiterate. Is there not a way where, perhaps with assistance from a sysadmin, I can call Calendar.Read.Write.All so I can add the events to others' calendars? If not, what is the simplest tool to create an app that can achieve what I need to do? I thought I could use Power Automate but saw somewhere that it doesn't work with app roles.

Thanks