Authenticating REST service error

Hi, I want to send my project data to Google Bigquery. I’m using REST services for the same. I have the endpoint URL, but I can’t seem to get the authentication right. I get the following error :

{ “error”: { “code”: 401, “message”: "Request is missing required authentication credential. Expected OAuth 2 access token, login cookie or other valid authentication credential. See", “errors”: [ { “message”: “Login Required.”, “domain”: “global”, “reason”: “required”, “location”: “Authorization”, “locationType”: “header” } ], “status”: “UNAUTHENTICATED” } }

I have tried adding using custom HTTP header option with :

Name as Authorization and Value as Bearer <Google_API_KEY>

as well as :

Name as Authorization and Value as Apikey <Google_API_KEY>

What would be the solution to this?