Once you have downloaded the setup install it on your local computers.
Start the LiveZilla Server Admin application (you can find an icon on your desktop).
Select Update existing LiveZilla Server.
Follow the wizard until you reach the FTP inputs page and enter your FTP login details.
Please use the Select button to choose the folder of your initial LiveZilla server installation. Please don't skip this step and make sure that you have selected the folder of your initial installation as target folder.
Upload the files, run a server test and validate the URL of your server.
Validate your database, all required updates of the database structure will be applied automatically.
Please check your LiveZilla Server page for warnings or error messages. That's it. :)