Make sure you have previously registered on https://www.twitch.tv/
To setup Reddit social login, go to https://dev.twitch.tv/console/apps/ and click on Applications
Then click on Register Your Application
Fill out required fields such as the application Name and OAuth Redirect URLs: https://yourwebsitedomain.com/wp-login.php/?action=social_login_authenticated&provider=TwitchTV
Select Website Integration for Category.
Click on Create and at the next page you can find your Client ID and Client Secret there.
Enter the Client ID and Client Secret keys into Social Login plugin configuration and you’re good to go.