I made the HelloWorld Greeting App. How do i make an API call?

[Aleksandr Gembinski]

I am trying to fetch some data to confirm things are working. But the tutorial ends and there are no next steps.

I can see the AP library loads and it makes calls on my behalf. But if i try and make the same calls manually the AP library is appending "&r=123456789" and my calls fail.

Do i need to authenticate something? I can hit the same urls in my browser and see data, but when i try and fetch them from code i get 403 forbidden.

I created an OAuth client ID and secret but where do i put them in the Greeting App?

I wish the tutorial had the final step:
Get some data :(