Change default format for date field on user register form

I'm new to Drupal 8. In the user registration form, i've added a Date field via manage fields in user account settings. However, I need to customize this field and change its format. I tried 'manage display' but it's not taking effect. Is there something I'm missing. (Ideally, it should look and behave just like field datetime in Drupal 8 webform)

Appreciate any help given.

Thanks