Head over to IceCoder to download the script.
Now download it and upload the zip file to your hosting..
Now visit unzipper.php on your site once uploaded or using the built in extract function in the file manager.
I'll use unzipper.php
Extract the script and launch it in your browser
Choose a password so only you can edit your website!
Now login with your password
Now you can fully edit your site with a decent code editor in your browser live! You can make changes and save as well
Any questions do shoot them over!