Check out this learning path on creating a custom login: https://academy.mendix.com/link/module/183/lecture/1419/3.6-Custom-Login-Page
Hello,
You can create login page by following below link,
https://academy.mendix.com/link/module/183/lecture/1419/3.6-Custom-Login-Page
or
https://www.youtube.com/watch?v=ePuS-grmcXw&t=405s follow this youtube link.
Thank you.