What would I initially do to make a basic calculator app for a desktop computer without watching a code along video?

No Link here. I just want feedback on a question.

Learn a programming language that has bindings to native GUI toolkits - this is most of them (C, C++, C#, Java, Python, JS via Electron, etc etc). Learn the GUI toolkit (ex. QT, GTK+, wxWidgets, Sciter, Electron, Cocoa, etc). Build the calculator. Simple!

You are venturing off into another realm of codes.
But the underlying idea is that you need some form of GUI component.

Java have libraries that can accomplish that. You’ll have to learn some OOP if you don’t already know it.

Just to clarify here, this is not a great question. We have no idea what you know, we have no idea what you’ve tried, and though I was flippant with my first answer, it is correct in that literally that every major programming language has access to at least one GUI toolkit, other languages have many written for them (C or C++, for example). But we have no idea what you know, so we can’t give you useful answers.

I’ve never made one, but I suppose the first thing to do is to find out how a calculator works as data is input. What is its logic?
After that, find out what the calculator does with each input. It would need to put each number somewhere in memory and then wait for further numbers and/or operations and listen for the equals button.

Perhaps the most basic calculator would be a text-based one. Once the text calc works, you could make a GIU from CSS divs and have javaScript, for example listen for key and mouse actions. The program will populate a div to display digits as the user input and the final result.