First, go to the Identity Providers left menu item and select Github from the Add provider drop down list. This will bring you to the Add identity provider page.
To enable login with Github you first have to register an application project in GitHub Developer applications.
Click the Register a new application button.
Register a new application
You’ll have to copy the Redirect URI from the "Keycloak Add Identity Provider" page and enter it into the Authorization callback URL field on the Github "Register a new OAuth application" page.
You will need to obtain the client id and secret from this page so you can enter them into the Keycloak "Add identity provider" page. Go back to Keycloak.
Enter the client id and secret.
Enter a default scope user:email and click save