Using TextWrangler to edit files over FTP/SFTP
First, from the File menu select Open from FTP/SFTP Server...
Then, put in the information for the Dreamhack (or other server) you are hosting on. For dreamhacks, the server name is hack.dreamwidth.net and the username is your hack username, always in the form of dh-USERNAME, and you should know your password.
Then, you'll be able to browse and find whatever file you want to edit like normal.