Authentication failed

i followed every steps but while running the curl command i am getting this error

You sure that’s your access token not app secret?

that is not app secret .that is the access token i get from postman

You are trying to create pins …right? You have to use appropriate URL for creating pins. Use the link given in task 3 …Pinterest API explorer.

please tell how to get board id
and i run the above curl command mention in the document for getting board id

Did you tried sending the request via Postman?
Import the cURL in Postman, provide the necessary parameters and see if that works.
Check these links for more details.