Add a country for shipping address otherwise won't work.
pip install django-oscar-paypal
https://django-oscar-paypal.readthedocs.io/en/latest/
https://django-oscar-paypal.readthedocs.io/en/latest/express.html#getting-started
First create a normal paypal account. Then go to the link.
https://developer.paypal.com/developer/accounts/
Click on edit for above business sandbox account. Copy API credentials to put it in settings.py