To use this functionality, first create the service account you want to impersonate. Then grant users that you want to be able to impersonate this service account the roles/iam.serviceAccountTokenCreator role on the service account resource. Then, you also need to grant the service account the same role on itself. This allows it to create short-lived tokens identifying itself, and allows your human users (or other service accounts) to do the same. More information on this scenario is available here.
Once you've granted the appropriate permissions, you'll need to enable the IAM Service Account Credentials API. Enabling the API and granting the role are eventually consistent operations, taking up to 7 minutes to fully complete, but usually fully propagating within 60 seconds. Give it a few minutes, then add the impersonate_service_account option to your BigQuery profile configuration.