To create a new service account, go to the Credentials section in APIs and Services; then click on Create credentials and use the Service account key option. Choose JSON format for the credentials as shown in the next screenshot, and choose New service account in the Service account dropdown. Specify a friendly and meaningful name for the service account and select the appropriate roles for the service account for the various services needed for the application. For this demo, choose the BigQuery Data Owner role for this service account.
Click on Create and the JSON file will be generated and downloaded:
Store the JSON file for the service account securely. The file cannot be regenerated for the same account after the initial creation of the credentials. It is better to create one service account per application in your enterprise to track and disable applications that overuse resources on Google Cloud.