You have finished the creation of the network restriction GPO.
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 DENY USB WRITE 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 connect a USB storage drive to the computer and try to save a file.
Your computer should automatically deny the write access to USB storage device.