You have finished the creation of the require GPO to lock the screen of windows computers.
But, you still need to enable the use of your new Group Policy.
On the Group policy management screen, you need to right-click the Organizational Unit desired and select the option to link an existent GPO.
In our example, we are going to link the group policy named LOCK WINDOWS SCREEN to the root of our domain named TECH.LOCAL.
After applying the GPO you need to wait for 10 or 20 minutes.
During this time the GPO will be replicated to other domain controllers that you might have.
After waiting 20 minutes, you should reboot a user's computer.
During the boot, the computer will get and apply a copy of the new group policy.
To test the configuration, you need to login on a domain computer and do nothing for 600 seconds.
Your computer screen should automatically lock itself after 600 seconds.