This is where you can change the user's password:

 

 

Please be aware that this tab is hidden if the edited user is authenticated using either an external user database or Active Directory, i.e., if the user has the Is external user or Is domain user property enabled on the General tab of the user editing interface and the application is configured to use Windows authentication.

 

Page url: http://devnet.kentico.com/docs/5_5r2/contexthelp/index.html?password_tab.htm