Making drawings with code ( first lesson)

ok my son is 9 years old I like to teach him and help him with computer programmings skills So we select lesson one. 'making drawings with code' ( the circle)

Now I would like him to write and make his own circle while listening to the teacher.

But it doesn't say where to put the code? There are lots of tips and tricks but it doesn't really say where to write? is it in a separate browser tap? a javascript secondary browser?

This is a bit of a miss to get kids directly involved when there is absolutely no hint where to write ur code? So perhaps also for the parents this could have a 'where to start' hint!
the rest looks great