For this tutorial, we will be using the FTP client called WinSCP.
Install the client with the default options

Using the 'New Site' popup

Choose the file procol "FTP"
Encryption: No encryption
Host name: Your Gameserver IP address
Port: 821
Username: Your Game Panel username (email address)
Password: Your Game Panel password

Once all those settings have been entered you can click login and connect to your server !