To use Social Login to allow sign-in using Facebook, a Facebook client has to be created first. 

These steps will help you set up an OAuth Client within Facebook.

Creating an App

1. Go to Facebook Developers Page.
2. Sign in using your Facebook account credentials. 
3. Click My Apps in the top-right corner.
   
   
   
   
4. Click Create App.
5. On the next screen, choose Authenticate and request data from users with Facebook Login. Click Next.
   
   
   
   
6. Choose No, I am not building a game, then click Next.
   
   
   
   
7. Provide an app name and app contact email (to which Facebook will send emails regarding the app) and click Create app.
   
   
   
   
8. Your app will be created, and the following page will open. Choose Customize adding a Facebook Login button under Customize this app.
   
   
   
   
9. Click Go to settings under Settings.
   
   
   
   
10. Enter the redirect URI obtained from the Zoho Sites Member Portal page in the Valid OAuth Redirect URIs box, and click Save changes.
    
    
    
    
11. Click Go back, scroll down, and click Add next to Email under Permissions.
    
    
    
    
12. Click Go back in the top-right corner. Choose Dashboard from the left sidebar.
    
    
    
    
13. Select Review and complete the testing requirements.
    
    
    
14. Ensure the email and public profile are listed on this page and confirm the details. 
15. Go back and choose Business Verification under Review.
    
    
    
    
16. Click Start Verification if you have a business account with Facebook or Meta.
    
    
    
    
17. Choose App Review and click Edit under the Current requests tab.
    
    
    
    
18. A popup will appear if you do not have a verified business ID, prompting you to complete the verification and return to the page to finish the verification.
    
    
    
    
19. You can follow the steps in this link to complete the business verification.
20. Complete the Business verification and App Review to proceed. 
21. Publish the app by clicking the Publish button.
22. Choose App Settings on the left sidebar and select Basic.
    
    
    
    
23. Enter the app domain and privacy policy URL on this page. An app domain is the domain of your website and privacy policy would be a page listing the privacy policy of your website.
    
    
    
    
24. Upload an App icon, enter the User data deletion instructions URL, and choose the Category of your app.
    
    
    
    
25. Copy the App ID and App secret displayed on the page.
    
    
    
    
26. Switch to Zoho Sites and configure Social Login by using the App ID and App secret in the above step.