In my case, I needed to perform some extra steps.
After installing the driver and MP Navigator applications for Windows 8.1 (and then rebooting), the MP Navigator app still presented me with an error when I tried to open it. After plugging in the USB cable from the printer into my PC, however, Windows was able (after a minute of apparently doing nothing) to detect and install the correct drivers.
These were the steps I followed but I don't know whether they are all necessary or not.