Make sure that you see "Code" here if you run Python code
Put your mouse here and you will see:
Press "Shift+Enter"
You have successfully run your first Python code
It is successful when you see a number is assigned to the cell (here the number is 1).
Choose the third cell
Pull down the "Code" menu and choose "Markdown"
Change the cell type from "Code" to "Markdown"
The third cell now becomes a "Markdown" cell where you can write notes.
Double click the third cell
Write down your first note
Press "Shift+Enter"