Google ConvertLIT GUI
I suggest trying it on a LIT file without DRM first, e.g. from Baen Free Library
. I have instructions for converting a DRM-free LIT to MOBI in Baen format upgrade in the works
. You don't want MOBI, but this might help if you want to use BookDesigner. Or just try lit2lrf on a DRM-free LIT once you have ConvertLIT installed.