There is a detailed guide available. See moving from 2.4 to 2.5.
In your case you do not see your new users because the menu item show a page with a list of Administration.Account entities (inheriting from System.User) instead of System.User objects.
We have added the Administration module in 2.5 because the System module is now readonly. The administration module contains all default forms for user management and system administration. You are allowed to change these forms yourself.