With mycms 6 you can edit the themes online.
Go to the admin panel in the themes page.
Select what theme you want edit, then click the "Info" button.
In the left you can view the screenshot, in the middle you view the files in the cms and in the right you view the "Edit in Code Editor" button.
Click on it and now you view the editor.
If you click on the gear on the top right you can view the menu.
If you click on a file you open it.