In the Cloud Console, go to the Create service account keypage.
From the Service account list, select New service account.
In the Service account name field, enter a name.
From the Role list, add the following roles
BigQuery Job User
BigQuery Data Viewer
BigQuery Metadata Viewer
Click Create. A JSON file that contains your key downloads to your
computer.
The Role field affects which resources your service account can access in
your project. You can revoke these roles or grant additional roles later. For
more information, see
Granting, changing, and revoking access to resources.