Ehmz... I don't know what you need, but normally it's not needed to edit Grub when using Directadmin.
You can get to those folders using SSH with an SSH client like for example Putty. It's like console. I didn't know Bitvise but I see now that's also an SSH client.
You should be able to login and go there.
Which Linux distro are you using and what do you see after logging in via SSH?