My guess is that you use it like Windows Explorer. The right pane at http://a.fsdn.com/con/app/proj/discfit/screenshots/306607.jpg has the set so you would run your CD/DVD recording app and then make a Data DVD then select the set and then lasso all the files or try control+A and then drag and drop them into the pane on the recorder app that allows dropping from Explorer.
Again, it looks abandoned so hope this helps,
I found a great program, DiscFit, to assist in selecting file for buring to a DVD
My question ... How do I drag the files to my DVD burning software. I've tried right click, alt click, standing on my head and can't seem to get the flles to move ?
From the website....Arranges a big set of files or directories in order to use the minimum number of phisycal media (CD, DVD, BD...) pieces. You can drag the resulting sets directly over your burning software (Nero, DVD-go...)