This module provides authorization capabilities so that authenticated users can be allowed or denied access to portions of the web site. mod_authz_user grants access if the authenticated user is listed in a Require user directive. Alternatively Require valid-user can be used to grant access to all successfully authenticated users.
Uncomment this line in /etc/httpd/conf/httpd.conf:
LoadModule authz_user_module modules/mod_authz_user.so
Then restart apache.