And you don't know how to use that? You need an address, a username and a password, all if which your host should have given you. Then you need an FTP program. FileZilla is a good and free one if you are on Windows.
http://filezilla.sourceforge.net/It's pretty simple. You create a bookmark of sorts with your details so you don't have to enter them every time. Then you just click on it to connect. You'll see two windows. The left one (usually) showing your own HD and the right one the server. You can drag and drop files from one side the other and they will be transferred up or down. You can do this in other ways too, but that depends on the program and how you configure it. Examine the buttons and menu commands and you'll soon find what you need.