You'll need to purchase hosting to start. I suggest using Host Gator as they are good and reliable for an affordable price.
Then you'll need to update your domain name, nameserver information. Instructions on how to do that are generally included when you purchase hosting.
Next you'll need to upload (FTP) all the files to your hosting account. A good free FTP program is FileZilla should you need one.
Next create your MySQL database in the control panel, enter the details into config.php.new and rename it to config.php
Run the install script