Upload your files in your Premium-Zone, and you will get points for downloads of your files. You can then convert your collected points to free premium-accounts. (Check "Convert points" in your premium-zone.) You can also extend your own premium-account for free. You will get one point per download if the downloader is a free-user AND your file is bigger than 1 MB AND the downloader has generated less than 5 points in the last three hours. This rules have been introduced to protect us from abuse.