Twitch works similar to Facebook (OAuth).
Register a new application in the connections tab of your Twitch settings page, set the callback URL to http://example.com/complete/twitch/ replacing example.com with your domain.
Fill Client Id and Client Secret values in the settings:
SOCIAL_AUTH_TWITCH_KEY = ''
SOCIAL_AUTH_TWITCH_SECRET = ''
Also it’s possible to define extra permissions with:
SOCIAL_AUTH_TWITCH_SCOPE = [...]