Using MIDI

I have MusicScore 9.5, and Windows 7. I have a Yamaha PSR-E203/YPT-200 keyboard with MIDI. I have the MIDI/USB cable, and Windows 7 correctly installed the dirver. How do I get MuseScore to play through my Yamaha? I've tried to find information here, but it is not helpful. The "handbook" doesn't give what I would consider basic information for making MIDI work. Your assitance will be appreciated. Thank you.