Hi @tharindukw96,
By default, the Universal login page would be hosted on a site like https://<YOUR_TENANT>..auth0.com/
You can change this by configuring a Custom Domain to allow you to host the universal login page on a subdomain of your own domain.
e.g. for the domain acme.com, you could have account.acme.com.
This universal login page can be used for all of the applications you configure, you just need to begin an /authorize call with a “redirect_uri” back to the app being logged into so the user is sent back to the right place after authentication.
Please see here for some more information on the various authentication flows available: Authentication and Authorization Flows