I believe you have to go into the users menu - click your name (admin, or whatever it's called) and there should be a checkbox on the left that says "use WYSIWYG", just uncheck and save. Sorry I cant be more specific, I don't have the actual screen in front of me - but that's how it's done
Go to Users when u login the admin panel and then click on the edit button in front of the user account...there at top u will see Use the visual editor when writing ...just uncheck it