Please go to the URL www.console.cloud.google.com and login with the account details.  If you have more than a project, choose the project on the top middle, beside to the

Please follow the instructions given in below screen with numbers

Then Create Service Account -> Service account name -> create

Select a role which you wanted to provide -> continue -> create key -> choose json – create.

• We can assign any number of roles to this account
• Once the last step completes, it will give you one json file which can be used while creating BigQuery datapoint.