From your Google Cloud Console, you need to create a service account and assign it permissions to access BigQuery.
Note that when generating the key file, select the JSON type and later use it when setting > up the data source.
From all the settings the mandatory ones are the key file and the Project ID.
If you're using the predefined roles in BigQuery you need to use the admin role, as this is the only role that can create queries and list tables.
If you want to create your own role, the permissions you need to assign are: bigquery.jobs.create bigquery.jobs.get bigquery.jobs.update bigquery.datasets.list bigquery.datasets.get bigquery.tables.list bigquery.tables.get bigquery.tables.getData