Replace link and text with correct values. Make sure to wrap link in "li" tag.
If after editing template files you do not see changes, go to admin control panel and click "purge cache" button on admin control panel's main page.
If after editing template files your header is messed up, you most likely have used incorrect editor that messed up code. Use only simple text editors to edit template files, such as Notepad or TextEdit. Do not use FrontPage, Expression or Dreamweaver unless you know how to use them.
If you have any questions or ran into problems, please post your questions on support forum.