When you access an FTP server in Firefox, the address will begin with ftp:// (e.g. ftp://ftp.mozilla.org/). File and folders are listed as if you were browsing a computer hard drive.
Clicking on a folder will navigate you to the contents of the folder.
Clicking on a file will make Firefox try to display that file. (As if you clicked on that a link to that file on any webpage.)
To download a file:
Right-clickHold down the Ctrl key while you click
on the file name.
Select Save Link As....
You will be prompted to choose where on your computer to save it. Choose a location, and click Save.
FTP servers that require a username and password
By default, Firefox accesses FTP servers anonymously. To provide a username and password, put the username before the server name in the URL, and divide it with an @ symbol.