You post files to the host computer using FTP (File Transfer Protocol). Although you could theoretically do this using just text commands, you could also theoretically perform a root canal on yourself. Almost everyone uses a program with a GUI (Graphical User Interface).
While you have dozens of FTP programs to choose from, I suggest FileZilla. It's free.
When using a Mac, I prefer CyberDuck. You can find it at http://cyberduck.ch/.
Once you have an FTP program installed, you will need to log onto your host site and upload the files. To logon you will need your user name and password, which you get from the hosting company. Having successfully logged on, you will need to get into the correct directory for your website (usually something like "public_html" -- your hosting company can tell you which directory it is).
Assuming you have tested your pages, load up any files and subdirectories. Save the index.htm or index.html file for last. It is your home page, and you should have the rest of the site in place before it goes up.
Having loaded your files up to the host, your site has now gone "live". Before you celebrate, test everything to make sure it is there and working properly. If so, Congratulations! You have a web site.
