You'll need the following info:
The address of the server: i.e ftp.anandtech.com
A username/password, probably assigned by whoever runs the FTP.
Port number (default is 21, but some servers use other ports).
Once you know that, it's simple. Enter the above info in FileZilla and hit Quick connect. Then you'll see two explorer-style windows where you can drag stuff from one to the other (if you have the proper read/write permissions).