You'll need an FTP client, by the sounds of it. //you could do it from the command line if you wanted, though
If you use windows, download smartFTP from
here
Install it as usual, then run it
at the top of your screen you'll see:
Adress, Login, Password, Port with boxes for each bit of information
an example would be either an IP or a host for the address:
192.168.2.1 or catwoman.com, for instance
Login is the username you were supplied with
Password is the password you were supplied with
Port should be set to 21, unless you were advised to use another one
//you'll need a different FTP client if you're on a Mac...dunno a free one off the top of my head