Uploading to google code?
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You can create a Google Code project for free and then choose your favorite version control system, e.g. SVN or Git, for that project. Then you simply "commit" all files related to your project into the code repository and that's it. Well, Git will also need a "push" operation to actually upload the files to the server. Once you are done, others will be able to checkout/clone your code from the repository - and they even can commit/pull their changes.
If, however, you wish to provide direct "downloads", then Google Code probably is not a good choice. They currently allow projects to upload files and offer these files as public downloads, but they are going to remove that feature very soon! Go for SourceForge or Bitbucket if you need that.
Also, GitHub is a valuable alternative to Google Code you should consider.
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If you are not familiar with version control systems yet, start here:
http://git-scm.com/book/en/Getting-Started-About-Version-Control