Appsfuel uses OAuth v2 for Authentication check the official docs too.
Sign up at the Appsfuel Developer Program
Create and verify a new app
On the dashboard click on Show API keys
Fill Client Id and Client Secret values in the settings:
SOCIAL_AUTH_APPSFUEL_KEY = '<App UID>'
SOCIAL_AUTH_APPSFUEL_SECRET = '<App secret>'
Appsfuel gives you the chance to integrate with Live or Sandbox env.
Add 'social.backends.appsfuel.AppsfuelOAuth2Sandbox' into your AUTHENTICATION_BACKENDS.
Then you can start using {% url social:begin 'appsfuel-sandbox' %} in your templates
Define the settings:
SOCIAL_AUTH_APPSFUEL_SANDBOX_KEY = '<App UID>'
SOCIAL_AUTH_APPSFUEL_SANDBOX_SECRET = '<App secret>'