Download the administration module: https://appstore.home.mendix.com/link/app/23513/Mendix/Administration-module
into your project. Inside are all the pages to create accounts and add roles to account by an admin.
Actually no. Mendix systems already have a authentication. You can search for administration module, and use it to create or update the users. To test this, add in your navigation a page of Administration Module (App Store Modules > Administration > User Management > Admin > Account_Overview). This page allows you to see how create and update a user.
You can create your own user administrator too, and can even create a self sign in (but is way mor complex, and you have to pay attention to your total users number).
Alternatively, you can use Single Sign On too manage the accounts in your company, if you have SSO.