To be able to use Google Indexing API Please follow steps :
1. Have a Gmail account and go to Google Cloud Console
- First you need to create new project
- Go to Service Accounts and create one by select permission owner. After done you will get an email
- Then click on KEYS to create key
Key will automatic download to your computer please keep that Json key and email to use on next steps
2. Add user owner to Google Search Console
Please copy email from service account and add to your search console user as ownerpip install --upgrade oauth2client
If you face any issues don't hesitate to comment.