Cannot get “Editing” page – only “Browsing” page

I am trying to edit the sidebar.php – to place the code for Feedburner. I went to Manage> Files and in my blog http://www.dorismollerhairstyhling.com/blog I can only – and only- get the “Browsing” page which does not have an “Update File” button that the “Editing” page has. Would you please tell me how I can get to the “Editing” page.