This guide will walk you through how to setup OAuth2 for API access using your own credentials using service accounts. These steps only need to be done once, unless you revoke or delete your OAuth2 credentials.
Step 1 - Creating OAuth2 credentials
Generate a service account ID and a *.JSON file by following the linked instructions, then come back to this page.
Step 2 - Setting up the client library
Set the private key JSON file path and delegate account ID in your
configuration. If you're using an ads.properties file, add the following:
api.googleads.serviceAccountSecretsPath=PRIVATE_KEY_FILE_PATH
api.googleads.serviceAccountUser=DELEGATE_ACCOUNT
See the configuration guide for additional details.