Hi Andrew,
It works very similar to the freerouting.net website. In KiCad pcbnew, you export your board layout as a Specctra design (.dsn) file (File Menu:Export). Then, instead of going to the web site to run the autorouter you run FreeRouter on your local machine. The "Open Your Own Design" button opens a dialog box that you use to locate the .dsn file you just created. Once located the board layout should open in FreeRouter. You can then run the auto router, manually route traces, etc., just like the freerouting.net website. When you are satisfied you then export a Specctra sessions (.ses) file from FreeRouter. Back in pcbnew you import the Specctra sessions file (File Menu:Import) and that updates the board layout with the traces that you created in FreeRouter.
If I get a chance I will make some simple files.
Thanks for trying out the Windows 8.1 version and letting me know you go it going.
Happy Routing! Michael