Explain better - unclear what to do and look for in these instructions

Section 11. Show Notifications should be explained more clearly. At: "Send a notification to your device" you say, "To send a notification, you'll need to send the following HTTP request:" What does that mean? Paste the code in the terminal?? Please explain better for newbs like me. Thanks!

Also, once we do that, what should we expect? A pop up notification? Or are we just looking at the response code? What should the response code say to know that it worked? Or do we have to do the next step before we expect anything. What should we expect from the next step? How to read the response code?