In order to Add a login provider :
- Click on =+ icon
- Select Add Provider
- Select Identity Provider
- Enter your APP ID, APP Secret Key, APP key (APP Key field is only required for providers which requires APP Key/Consumer Key such as Twitter, LinkedIn, etc)
- Click on the Create Button
For Callback URL :
- Click on Menu icon
- Select Providers
- Click/Hover on Provider Options
- Select Edit
- Copy Callback URL