Couple of ways
There are a couple of ways to do this. One, you can edit the file using the actual screen itself. Connect the keyboard to the terminal CPU backplate, and click Esc 3 times. This will bring up the terminal menu. If you don't already have an offline archive file, then I'd use this method. Then when your changes are complete, suck the file out of the terminal to back it up.
If you want to use the offline editer, there are a few things that you need. I'm by no means an expert, but I do know that the software needs to sit on your harddrive, it will not run from network location. We use an application called TeraTerm Pro to upload and download the files to the terminals. I am not sure where we got it, just that it is what we use. I'll look into this more here. In the meantime, I'd try to make the changes right on the controller if possible.