Java Compilation: Catching errors

I cannot understand how to do the first part of instructions. It says In the terminal, type this command: javac Compiling.java

Can someone point out where to type this because I am confused? What terminal? I typed it everywhere I could and it wont work. Link to exercise:

https://www.codecademy.com/courses/learn-java/lessons/hello-world-java/exercises/compilation-catching-errors?action=resume_content_item


The red arrow is where you type terminal commands. Happy Coding!