You can use any FTP client uploading your content to your Lightburner account. The FTP credentials were set to you in the “Welcome” email. They also are listed on the “Upload” page once you are logged into your LB account.
Please note that you should upload files into “/upload” folder, not in the root “/” folder of your Lightburner’ FTP account.
The files that resides in other but “/upload” folder will never be taken by the system and will not appear in your Lightburner account.