Get access token for google spreadsheet

Question

I need to know what is the exact API and parameters to write the data into Google Spreadsheet.

I am new to Google APIs. I am trying to integrate one of the SAP product ByD with google spreadsheet. So I need a REST URL and description.

I understood that, (https://developers.google.com/identity/protocols/OAuth2WebServer#handlingtheresponse)

1. Get Authorization code
2. From (1), Get Token Value
3. Call Write API along with Token Value.

Is this correct? Or any detailed step by step proceeder documentation?

I have tried to access authorization code as shown in the below screenshot. But it is returning 400 Bad requests

.

Regards Sankaran A