Not able to open in browser IDE

Can you please guide me to open in browser IDE ? Where should I add my script ?
Screenshot by Lightshot

How to open IDE ?
Thank you

post a screenshot. we need the whole context to help. my guess is that you enter the command in the file editor rather than the terminal area. it might be good to redo the lesson where the ide is presented

Thank you for your reply.
I got it from where should i open the IDE . From chapter 2