Contact your web host. They probably have an easy way to publish/upload your web pages.

Otherwise, there are plenty of FTP programs on the market - freeware, shareware etc - CuteFTP, WS_FTP to mention a couple.

But you will still need to contact your web host in order to get the information on how to connect to your web site using FTP. So the simplest approach is most likely to use your web host's upload function.