Hi Biswajit Kar,
To Enable authentication in your own web app by using Azure AD B2C :
This article shows you how to add Azure Active Directory B2C (Azure AD B2C) authentication to your own ASP.NET web application. Learn how create an ASP.NET Core web application with ASP.NET Core middleware that uses the OpenID Connect protocol.
Use this article in conjunction with Configure authentication in a sample web app, replacing the sample web app with your own web app.
For more information: https://learn.microsoft.com/en-us/azure/active-directory-b2c/enable-authentication-web-application?tabs=visual-studio
To customize the UI elements refer step 4
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