As well as tracking down the murderer, your homework tonight (and for the rest of your lives, really) is to get as comfortable with the command line as possible.
Read and work through one or more of the following, and revise these periodically throughout the course:
- https://www.codecademy.com/courses/learn-the-command-line/lessons/navigation/exercises/your-first-command
- https://www.learnenough.com/command-line-tutorial
- http://linuxcommand.org/tlcl.php - a comprehensive textbook
- http://en.flossmanuals.net/command-line/
- https://quickleft.com/blog/tag/command-line/page/4/ (reverse chronological order, start at the bottom)
- https://en.wikipedia.org/wiki/The_Unix_Programming_Environment - the classical text on Unix
- https://en.wikipedia.org/wiki/In_the_Beginning..._Was_the_Command_Line - Why bother with the command line
There are many other resources, videos, online courses etc. Find what works for you.