Please provide a link to the exact tutorial you are following. Are you using SiteAssist Pro? Assuming you are running the wizard, then trying to update the template yourself, you can just use Dreamweaver's built in functionality to do so. Keep in mind, if you re-enter the SiteAssist Pro wizard after modifying the template yourself, it might overwrite your changes. Using the mystyles.css will keep your css changes persistent even if you re-enter the wizard.