Here’s how you do that:
1. Create a service account for your Google BigQuery project.
After selecting your Google BigQuery project in your Google Cloud Console, go to ‘IAM & admin’ in the navigation menu, then select ‘Service accounts.’
Click the ‘+ CREATE SERVICE ACCOUNT’ button.
Name your service account.
Choose a Project role by clicking the ‘Select a role’ button.
Choose ‘BigQuery,’ then choose the ‘BigQuery Admin’ role.
Make sure you check the ‘Furnish a new private key’ box, and select the JSON format.
Hit ‘SAVE’ in order to download your JSON file. This will be saved in the folder selected in your browser settings.
2. Go to 'Link a new credential' and then select BigQuery from the data source list.
3. Paste your Big Query JSON file content.
4. The query page is displayed and you can now query the data you need.
How to link Big Query credentials (video)