1. You will need a Facebook user account
2. Go to https://developers.facebook.com/
3. Click on 
4. Register and Verify your account
5. Enter a name for your Facebook app
5. Click on “Add first product”
6. Choose “Facebook Login” in the list by clicking on “Set Up“:
7. Skip the forms by going to settings > basic in the left menu.
Here are the App ID and the Secret you will use in you app editor
- from the side menu >settings > apis
- copy and paste your “App ID” and “App secret”
8. copy the Callback URLs :
9. From the Facebook settings left menu, click on “Facebook Login” > “Settings” and paste the URLs then click on “Save changes”
10. In the App Domains field, left it blank. For Category, select “Communication“.
11. Click on “+Add Platform” and choose “Website“:
12. In the Site URL field enter "https://app.u3.net,https://*.u3.net”. Then save.
13. You can also add an app icon for your app. It’s not mandatory but your Facebook app will be more professional with an icon when the user will be invited to connect with his Facebook account. Click on “Save Changes“.
14. From the left menu, click on “App Review“:
15. Switch “Make 'app name' app public?” to “YES“.
16. You’re done!