Accessing Apigee Edge APIs require own credentials ? If so how to access this ?

[sahoosubhankar]

When I am executing any of the API in Apigee for example: (URL Removed by Staff) or (URL Removed by Staff) it is giving me this error in Postman :

"{
"error": {
"code": 401,
"message": "Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.",
"status": "UNAUTHENTICATED"
}
}"

Docs Link: "https://developers.google.com/explorer-help/"

How to resolve this error and how to get this APIs explorer own credentials ? Why we need Authentication here and what type of Authentication I need to get the API response ?