If you don't already, you need your domain name hosted on a Web server. There are hundreds of Web hosting providers to choose from. The company that registered your domain name might even offer hosting.
Once you have a Web host, the hosting provider should give you instructions for uploading files to the server. Generally, it is done with an FTP (File Transfer Protocol) program, such as WS_FTP or FileZilla, etc. (for PCs) or Fetch (for Mac's).
It is also common for hosting providers to offer uploading through built-in control panels that come with your plan, but it depends on the hosting company.