After you install the program and launch it you will need to input your account information, which we will provide to you upon setting up, in order to connect via FTP.
You will then find the file on your local computer (the left pane) and then drag it to the right pane (which is the server). It will then begin to upload. Depending on the file size, it may take a while. If you need more documentation on using the program, there is a good tutorial complete with screenshots located here: http://wiki.filezilla-project.org/Using#Connecting_to_an_FTP_server These files will be uploaded to a specified folder in the file manager.
After the file has been completely uploaded navigate to the media folder in the file manager. Once you have clicked on that folder click on the Synchronize Folder button in the file manager. This will make sure that the website 'sees' the file you just uploaded. See below screenshot for clarification.