It is only additional MPM for Apache web server.

To enable it:

=== For versions >= 2.4
1) Choose non-threaded MPM like prefork in: /etc/httpd/conf.modules.d/00-mpm.conf
2) Uncomment ITK in shipped: /etc/httpd/conf.modules.d/00-mpm-itk.conf
3) Then (re)start service: systemctl start httpd

=== For versions < 2.4
1) If you are use moderm systemd:
systemctl stop httpd.service
systemctl disable httpd.service
systemctl enable httpd-itk.service
systemctl start httpd-itk.service

2) If you are still using old sysvinit style:
Set HTTPD=/usr/sbin/httpd.itk in /etc/sysconfig/httpd and restart daemon:
service httpd restart


For more information about Apache refer to man and manuals in main httpd package