When I opened your file, I don’t see an active vertex.
You selected the parts whilst in face select mode, and one face is white, or a lighter shade of orange,
You now need to shift select one of the vertices, or the top edge in edge select mode, to make it active, white.
Also, you say scale in X in your question, the instructor says scale in Z.
If something is not quite working as it is in the lesson, rewind and double check your understanding.
This is something that we all do as a beginner, and can be a source of frustration.
Keep going, you will get there!
