In the site structure you should have a folder named CSSMenuWriter. In that folder you *should* have 3 folders:
Two of the folders are named as below, but you are looking to open the other one (its *probably* named cssmw).
In the other folder there will be a file named menu.php - its in this file that you will find the navigation points so that you can change what you need to do and then upload.
Hope that this helps