Find the network connections icon in the bottom right corner of the screen (near the clock). The icon can be in the shape of a computer display or wireless signal meter (you can see it on Step 10 of the Settings guide above).
Click that icon. In the appeared list click on any network connection.
After that, you will see another window with the connection list, click on the RealVPN connection (the connection name can be different, you have set it up on Step 5 of the Settings guide above).
Click the "Disconnect" button under the connection name.