These videos show how to create scripts (m-files) in MATLAB and in Octave.
How to create a script M-file in MATLAB, Robert Talbert:
How to Create a MATLAB Script, Mathworks: (The 1st 2 minutes are the most important.)
(This also mentions how to create "Live Editor" .mlx files. For most of the assignments in this course, that is more advanced than we need.)
Octave Programming Lesson 4.1 - Script File Basics, Hanshaw Virtual University